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 $216.59   9.704%   $237.6079   $237.61   $237.60   $237.60  
  Purchase #2 $170.82   9.334%   $186.7643   $186.76   $186.75   $186.80  
  Purchase #3 $69.27   3.322%   $71.5711   $71.57   $71.55   $71.60  
  Purchase #4 $112.54   6.339%   $119.6739   $119.67   $119.65   $119.70  
  Purchase #5 $112.49   5.372%   $118.533   $118.53   $118.55   $118.50  
  Purchase #6 $47.58   13.806%   $54.1489   $54.15   $54.15   $54.10  
  Purchase #7 $168.45   10.713%   $186.496   $186.50   $186.50   $186.50  
  7 purchase totals = $897.74       $974.7951   $974.79   $974.75   $974.80