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 $217.38   13.144%   $245.9524   $245.95   $245.95   $246.00  
  Purchase #2 $102.98   4.605%   $107.7222   $107.72   $107.70   $107.70  
  Purchase #3 $119.77   3.653%   $124.1452   $124.15   $124.15   $124.10  
  Purchase #4 $91.45   5.358%   $96.3499   $96.35   $96.35   $96.30  
  Purchase #5 $212.43   9.192%   $231.9566   $231.96   $231.95   $232.00  
  Purchase #6 $184.47   10.518%   $203.8726   $203.87   $203.85   $203.90  
  Purchase #7 $104.75   10.588%   $115.8409   $115.84   $115.85   $115.80  
  7 purchase totals = $1,033.23       $1,125.8398   $1,125.84   $1,125.80   $1,125.80