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 $148.26   6.265%   $157.5485   $157.55   $157.55   $157.50  
  Purchase #2 $229.38   10.520%   $253.5108   $253.51   $253.50   $253.50  
  Purchase #3 $94.99   10.376%   $104.8462   $104.85   $104.85   $104.80  
  Purchase #4 $44.34   4.362%   $46.2741   $46.27   $46.25   $46.30  
  Purchase #5 $111.41   11.690%   $124.4338   $124.43   $124.45   $124.40  
  Purchase #6 $243.48   7.149%   $260.8864   $260.89   $260.90   $260.90  
  Purchase #7 $62.97   6.840%   $67.2771   $67.28   $67.30   $67.30  
  7 purchase totals = $934.83       $1,014.7769   $1,014.78   $1,014.80   $1,014.70