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 $68.95   6.695%   $73.5662   $73.57   $73.55   $73.60  
  Purchase #2 $46.32   5.662%   $48.9426   $48.94   $48.95   $48.90  
  Purchase #3 $246.70   3.353%   $254.9719   $254.97   $254.95   $255.00  
  Purchase #4 $102.52   3.174%   $105.774   $105.77   $105.75   $105.80  
  Purchase #5 $58.55   7.504%   $62.9436   $62.94   $62.95   $62.90  
  Purchase #6 $216.50   8.341%   $234.5583   $234.56   $234.55   $234.60  
  Purchase #7 $75.33   7.818%   $81.2193   $81.22   $81.20   $81.20  
  7 purchase totals = $814.87       $861.9759   $861.97   $861.90   $862.00