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 $212.58   5.127%   $223.479   $223.48   $223.50   $223.50  
  Purchase #2 $172.96   5.245%   $182.0318   $182.03   $182.05   $182.00  
  Purchase #3 $12.68   10.124%   $13.9637   $13.96   $13.95   $14.00  
  Purchase #4 $199.49   3.564%   $206.5998   $206.60   $206.60   $206.60  
  Purchase #5 $168.41   8.873%   $183.353   $183.35   $183.35   $183.40  
  Purchase #6 $198.30   4.673%   $207.5666   $207.57   $207.55   $207.60  
  Purchase #7 $119.92   11.832%   $134.1089   $134.11   $134.10   $134.10  
  7 purchase totals = $1,084.34       $1,151.1028   $1,151.10   $1,151.10   $1,151.20