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 $62.94   6.512%   $67.0387   $67.04   $67.05   $67.00  
  Purchase #2 $92.38   12.797%   $104.2019   $104.20   $104.20   $104.20  
  Purchase #3 $166.36   7.747%   $179.2479   $179.25   $179.25   $179.20  
  Purchase #4 $199.46   6.520%   $212.4648   $212.46   $212.45   $212.50  
  Purchase #5 $21.93   3.667%   $22.7342   $22.73   $22.75   $22.70  
  Purchase #6 $154.50   4.712%   $161.78   $161.78   $161.80   $161.80  
  Purchase #7 $136.74   10.443%   $151.0198   $151.02   $151.00   $151.00  
  7 purchase totals = $834.31       $898.4873   $898.48   $898.50   $898.40