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 $85.69   11.482%   $95.5289   $95.53   $95.55   $95.50  
  Purchase #2 $202.38   3.829%   $210.1291   $210.13   $210.15   $210.10  
  Purchase #3 $55.40   11.445%   $61.7405   $61.74   $61.75   $61.70  
  Purchase #4 $66.30   13.733%   $75.405   $75.41   $75.40   $75.40  
  Purchase #5 $46.54   9.258%   $50.8487   $50.85   $50.85   $50.80  
  Purchase #6 $246.97   13.529%   $280.3826   $280.38   $280.40   $280.40  
  Purchase #7 $234.64   5.175%   $246.7826   $246.78   $246.80   $246.80  
  7 purchase totals = $937.92       $1,020.8174   $1,020.82   $1,020.90   $1,020.70