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 $40.95   5.653%   $43.2649   $43.26   $43.25   $43.30  
  Purchase #2 $90.43   5.436%   $95.3458   $95.35   $95.35   $95.30  
  Purchase #3 $134.78   6.843%   $144.003   $144.00   $144.00   $144.00  
  Purchase #4 $83.58   3.848%   $86.7962   $86.80   $86.80   $86.80  
  Purchase #5 $245.98   6.419%   $261.7695   $261.77   $261.75   $261.80  
  Purchase #6 $158.64   11.758%   $177.2929   $177.29   $177.30   $177.30  
  Purchase #7 $121.51   9.356%   $132.8785   $132.88   $132.90   $132.90  
  7 purchase totals = $875.87       $941.3508   $941.35   $941.35   $941.40