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 $56.62   10.501%   $62.5657   $62.57   $62.55   $62.60  
  Purchase #2 $136.87   8.123%   $147.988   $147.99   $148.00   $148.00  
  Purchase #3 $134.88   6.177%   $143.2115   $143.21   $143.20   $143.20  
  Purchase #4 $132.75   13.201%   $150.2743   $150.27   $150.25   $150.30  
  Purchase #5 $63.81   6.174%   $67.7496   $67.75   $67.75   $67.70  
  Purchase #6 $182.77   9.414%   $199.976   $199.98   $200.00   $200.00  
  Purchase #7 $173.78   9.460%   $190.2196   $190.22   $190.20   $190.20  
  7 purchase totals = $881.48       $961.9847   $961.99   $961.95   $962.00