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 $48.50   9.669%   $53.1895   $53.19   $53.20   $53.20  
  Purchase #2 $128.55   5.799%   $136.0046   $136.00   $136.00   $136.00  
  Purchase #3 $116.99   8.473%   $126.9026   $126.90   $126.90   $126.90  
  Purchase #4 $106.46   11.868%   $119.0947   $119.09   $119.10   $119.10  
  Purchase #5 $103.56   9.450%   $113.3464   $113.35   $113.35   $113.30  
  Purchase #6 $166.28   10.215%   $183.2655   $183.27   $183.25   $183.30  
  Purchase #7 $65.46   12.484%   $73.632   $73.63   $73.65   $73.60  
  7 purchase totals = $735.80       $805.4353   $805.43   $805.45   $805.40