Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $151.80   13.502%   $172.296   $172.30   $172.30   $172.30  
  Purchase #2 $238.56   5.186%   $250.9317   $250.93   $250.95   $250.90  
  Purchase #3 $233.97   5.708%   $247.325   $247.33   $247.35   $247.30  
  Purchase #4 $166.33   13.549%   $188.8661   $188.87   $188.85   $188.90  
  Purchase #5 $241.30   7.727%   $259.9453   $259.95   $259.95   $259.90  
  Purchase #6 $119.92   5.566%   $126.5947   $126.59   $126.60   $126.60  
  Purchase #7 $195.60   11.433%   $217.9629   $217.96   $217.95   $218.00  
  7 purchase totals = $1,347.48       $1,463.9217   $1,463.93   $1,463.95   $1,463.90