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 $210.65   10.563%   $232.901   $232.90   $232.90   $232.90  
  Purchase #2 $95.44   9.866%   $104.8561   $104.86   $104.85   $104.90  
  Purchase #3 $66.66   11.589%   $74.3852   $74.39   $74.40   $74.40  
  Purchase #4 $146.56   3.572%   $151.7951   $151.80   $151.80   $151.80  
  Purchase #5 $57.73   9.203%   $63.0429   $63.04   $63.05   $63.00  
  Purchase #6 $48.47   8.762%   $52.7169   $52.72   $52.70   $52.70  
  Purchase #7 $70.36   9.211%   $76.8409   $76.84   $76.85   $76.80  
  7 purchase totals = $695.87       $756.5381   $756.55   $756.55   $756.50