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 $58.29   6.337%   $61.9838   $61.98   $62.00   $62.00  
  Purchase #2 $249.49   11.565%   $278.3435   $278.34   $278.35   $278.30  
  Purchase #3 $104.25   10.640%   $115.3422   $115.34   $115.35   $115.30  
  Purchase #4 $177.91   3.389%   $183.9394   $183.94   $183.95   $183.90  
  Purchase #5 $117.44   6.155%   $124.6684   $124.67   $124.65   $124.70  
  Purchase #6 $17.30   9.523%   $18.9475   $18.95   $18.95   $18.90  
  Purchase #7 $116.95   8.477%   $126.8639   $126.86   $126.85   $126.90  
  7 purchase totals = $841.63       $910.0887   $910.08   $910.10   $910.00