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 $214.47   9.585%   $235.0269   $235.03   $235.05   $235.00  
  Purchase #2 $63.63   7.198%   $68.2101   $68.21   $68.20   $68.20  
  Purchase #3 $190.68   3.622%   $197.5864   $197.59   $197.60   $197.60  
  Purchase #4 $248.51   11.741%   $277.6876   $277.69   $277.70   $277.70  
  Purchase #5 $214.79   9.508%   $235.2122   $235.21   $235.20   $235.20  
  Purchase #6 $95.29   12.358%   $107.0659   $107.07   $107.05   $107.10  
  Purchase #7 $199.33   11.354%   $221.9619   $221.96   $221.95   $222.00  
  7 purchase totals = $1,226.70       $1,342.7510   $1,342.76   $1,342.75   $1,342.80