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 $191.56   3.140%   $197.575   $197.58   $197.60   $197.60  
  Purchase #2 $81.94   4.518%   $85.642   $85.64   $85.65   $85.60  
  Purchase #3 $192.99   11.670%   $215.5119   $215.51   $215.50   $215.50  
  Purchase #4 $44.40   9.419%   $48.582   $48.58   $48.60   $48.60  
  Purchase #5 $225.59   13.503%   $256.0514   $256.05   $256.05   $256.10  
  Purchase #6 $152.88   3.610%   $158.399   $158.40   $158.40   $158.40  
  Purchase #7 $6.51   8.647%   $7.0729   $7.07   $7.05   $7.10  
  7 purchase totals = $895.87       $968.8342   $968.83   $968.85   $968.90