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 $202.89   5.795%   $214.6475   $214.65   $214.65   $214.60  
  Purchase #2 $109.29   11.580%   $121.9458   $121.95   $121.95   $121.90  
  Purchase #3 $199.45   8.153%   $215.7112   $215.71   $215.70   $215.70  
  Purchase #4 $212.84   13.797%   $242.2055   $242.21   $242.20   $242.20  
  Purchase #5 $54.99   13.592%   $62.4642   $62.46   $62.45   $62.50  
  Purchase #6 $98.66   9.403%   $107.937   $107.94   $107.95   $107.90  
  Purchase #7 $183.36   10.428%   $202.4808   $202.48   $202.50   $202.50  
  7 purchase totals = $1,061.48       $1,167.3920   $1,167.40   $1,167.40   $1,167.30