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 $65.47   5.650%   $69.1691   $69.17   $69.15   $69.20  
  Purchase #2 $149.65   3.428%   $154.78   $154.78   $154.80   $154.80  
  Purchase #3 $57.59   5.261%   $60.6198   $60.62   $60.60   $60.60  
  Purchase #4 $240.98   9.103%   $262.9164   $262.92   $262.90   $262.90  
  Purchase #5 $229.99   9.129%   $250.9858   $250.99   $251.00   $251.00  
  Purchase #6 $155.36   11.370%   $173.0244   $173.02   $173.00   $173.00  
  Purchase #7 $167.39   11.843%   $187.214   $187.21   $187.20   $187.20  
  7 purchase totals = $1,066.43       $1,158.7095   $1,158.71   $1,158.65   $1,158.70