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 $124.49   6.570%   $132.669   $132.67   $132.65   $132.70  
  Purchase #2 $247.71   11.582%   $276.3998   $276.40   $276.40   $276.40  
  Purchase #3 $18.48   4.752%   $19.3582   $19.36   $19.35   $19.40  
  Purchase #4 $32.81   10.734%   $36.3318   $36.33   $36.35   $36.30  
  Purchase #5 $230.45   10.566%   $254.7993   $254.80   $254.80   $254.80  
  Purchase #6 $187.59   4.462%   $195.9603   $195.96   $195.95   $196.00  
  Purchase #7 $16.34   10.150%   $17.9985   $18.00   $18.00   $18.00  
  7 purchase totals = $857.87       $933.5169   $933.52   $933.50   $933.60