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 $161.30   8.470%   $174.9621   $174.96   $174.95   $175.00  
  Purchase #2 $249.59   5.334%   $262.9031   $262.90   $262.90   $262.90  
  Purchase #3 $38.59   10.846%   $42.7755   $42.78   $42.80   $42.80  
  Purchase #4 $186.45   5.808%   $197.279   $197.28   $197.30   $197.30  
  Purchase #5 $54.39   12.521%   $61.2002   $61.20   $61.20   $61.20  
  Purchase #6 $46.38   10.250%   $51.134   $51.13   $51.15   $51.10  
  Purchase #7 $154.43   5.573%   $163.0364   $163.04   $163.05   $163.00  
  7 purchase totals = $891.13       $953.2903   $953.29   $953.35   $953.30