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 $88.50   10.237%   $97.5597   $97.56   $97.55   $97.60  
  Purchase #2 $53.92   11.198%   $59.958   $59.96   $59.95   $60.00  
  Purchase #3 $126.74   5.443%   $133.6385   $133.64   $133.65   $133.60  
  Purchase #4 $250.58   12.457%   $281.7948   $281.79   $281.80   $281.80  
  Purchase #5 $217.41   3.127%   $224.2084   $224.21   $224.20   $224.20  
  Purchase #6 $51.47   11.549%   $57.4143   $57.41   $57.40   $57.40  
  Purchase #7 $236.73   11.338%   $263.5704   $263.57   $263.55   $263.60  
  7 purchase totals = $1,025.35       $1,118.1441   $1,118.14   $1,118.10   $1,118.20