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 $86.46   9.848%   $94.9746   $94.97   $94.95   $95.00  
  Purchase #2 $32.69   10.874%   $36.2447   $36.24   $36.25   $36.20  
  Purchase #3 $166.63   12.573%   $187.5804   $187.58   $187.60   $187.60  
  Purchase #4 $31.89   7.331%   $34.2279   $34.23   $34.25   $34.20  
  Purchase #5 $120.71   3.778%   $125.2704   $125.27   $125.25   $125.30  
  Purchase #6 $61.30   8.237%   $66.3493   $66.35   $66.35   $66.30  
  Purchase #7 $110.25   7.654%   $118.6885   $118.69   $118.70   $118.70  
  7 purchase totals = $609.93       $663.3358   $663.33   $663.35   $663.30