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 $58.41   6.277%   $62.0764   $62.08   $62.10   $62.10  
  Purchase #2 $109.98   13.775%   $125.1297   $125.13   $125.15   $125.10  
  Purchase #3 $139.71   9.449%   $152.9112   $152.91   $152.90   $152.90  
  Purchase #4 $194.57   6.650%   $207.5089   $207.51   $207.50   $207.50  
  Purchase #5 $105.64   5.204%   $111.1375   $111.14   $111.15   $111.10  
  Purchase #6 $230.86   11.401%   $257.1803   $257.18   $257.20   $257.20  
  Purchase #7 $104.98   12.400%   $117.9975   $118.00   $118.00   $118.00  
  7 purchase totals = $944.15       $1,033.9415   $1,033.95   $1,034.00   $1,033.90