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 $109.85   6.265%   $116.7321   $116.73   $116.75   $116.70  
  Purchase #2 $232.62   8.202%   $251.6995   $251.70   $251.70   $251.70  
  Purchase #3 $46.70   7.820%   $50.3519   $50.35   $50.35   $50.40  
  Purchase #4 $188.86   12.748%   $212.9359   $212.94   $212.95   $212.90  
  Purchase #5 $129.84   8.687%   $141.1192   $141.12   $141.10   $141.10  
  Purchase #6 $225.99   4.733%   $236.6861   $236.69   $236.70   $236.70  
  Purchase #7 $117.65   6.354%   $125.1255   $125.13   $125.15   $125.10  
  7 purchase totals = $1,051.51       $1,134.6502   $1,134.66   $1,134.70   $1,134.60