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 $225.64   4.688%   $236.218   $236.22   $236.20   $236.20  
  Purchase #2 $178.77   5.828%   $189.1887   $189.19   $189.20   $189.20  
  Purchase #3 $9.94   10.750%   $11.0086   $11.01   $11.00   $11.00  
  Purchase #4 $166.58   9.441%   $182.3068   $182.31   $182.30   $182.30  
  Purchase #5 $32.76   8.125%   $35.4218   $35.42   $35.40   $35.40  
  Purchase #6 $29.85   7.143%   $31.9822   $31.98   $32.00   $32.00  
  Purchase #7 $68.33   7.357%   $73.357   $73.36   $73.35   $73.40  
  7 purchase totals = $711.87       $759.4831   $759.49   $759.45   $759.50