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 $52.77   10.723%   $58.4285   $58.43   $58.45   $58.40  
  Purchase #2 $188.28   9.467%   $206.1045   $206.10   $206.10   $206.10  
  Purchase #3 $164.57   13.161%   $186.2291   $186.23   $186.25   $186.20  
  Purchase #4 $29.45   11.833%   $32.9348   $32.93   $32.95   $32.90  
  Purchase #5 $135.72   12.571%   $152.7814   $152.78   $152.80   $152.80  
  Purchase #6 $204.69   13.594%   $232.5156   $232.52   $232.50   $232.50  
  Purchase #7 $173.93   11.551%   $194.0207   $194.02   $194.00   $194.00  
  7 purchase totals = $949.41       $1,063.0146   $1,063.01   $1,063.05   $1,062.90