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 $222.48   4.831%   $233.228   $233.23   $233.25   $233.20  
  Purchase #2 $63.50   10.692%   $70.2894   $70.29   $70.30   $70.30  
  Purchase #3 $43.79   10.129%   $48.2255   $48.23   $48.25   $48.20  
  Purchase #4 $142.69   13.342%   $161.7277   $161.73   $161.75   $161.70  
  Purchase #5 $228.82   10.104%   $251.94   $251.94   $251.95   $251.90  
  Purchase #6 $162.76   6.438%   $173.2385   $173.24   $173.25   $173.20  
  Purchase #7 $88.63   4.164%   $92.3206   $92.32   $92.30   $92.30  
  7 purchase totals = $952.67       $1,030.9697   $1,030.98   $1,031.05   $1,030.80