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 $176.69   10.472%   $195.193   $195.19   $195.20   $195.20  
  Purchase #2 $201.63   4.362%   $210.4251   $210.43   $210.45   $210.40  
  Purchase #3 $42.68   13.540%   $48.4589   $48.46   $48.45   $48.50  
  Purchase #4 $183.58   13.865%   $209.0334   $209.03   $209.05   $209.00  
  Purchase #5 $34.96   5.430%   $36.8583   $36.86   $36.85   $36.90  
  Purchase #6 $26.55   4.438%   $27.7283   $27.73   $27.75   $27.70  
  Purchase #7 $187.92   13.522%   $213.3305   $213.33   $213.35   $213.30  
  7 purchase totals = $854.01       $941.0275   $941.03   $941.10   $941.00