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 $65.26   8.866%   $71.046   $71.05   $71.05   $71.00  
  Purchase #2 $46.63   7.709%   $50.2247   $50.22   $50.20   $50.20  
  Purchase #3 $215.42   13.684%   $244.8981   $244.90   $244.90   $244.90  
  Purchase #4 $162.68   13.562%   $184.7427   $184.74   $184.75   $184.70  
  Purchase #5 $204.37   3.763%   $212.0604   $212.06   $212.05   $212.10  
  Purchase #6 $152.62   13.417%   $173.097   $173.10   $173.10   $173.10  
  Purchase #7 $32.63   8.754%   $35.4864   $35.49   $35.50   $35.50  
  7 purchase totals = $879.61       $971.5553   $971.56   $971.55   $971.50