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 $116.96   7.382%   $125.594   $125.59   $125.60   $125.60  
  Purchase #2 $49.96   8.820%   $54.3665   $54.37   $54.35   $54.40  
  Purchase #3 $30.61   5.631%   $32.3336   $32.33   $32.35   $32.30  
  Purchase #4 $87.73   5.782%   $92.8025   $92.80   $92.80   $92.80  
  Purchase #5 $136.73   6.166%   $145.1608   $145.16   $145.15   $145.20  
  Purchase #6 $236.36   3.269%   $244.0866   $244.09   $244.10   $244.10  
  Purchase #7 $90.74   6.630%   $96.7561   $96.76   $96.75   $96.80  
  7 purchase totals = $749.09       $791.1001   $791.10   $791.10   $791.20