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 $95.79   9.229%   $104.6305   $104.63   $104.65   $104.60  
  Purchase #2 $232.67   11.683%   $259.8528   $259.85   $259.85   $259.90  
  Purchase #3 $206.43   9.269%   $225.564   $225.56   $225.55   $225.60  
  Purchase #4 $143.71   13.824%   $163.5765   $163.58   $163.60   $163.60  
  Purchase #5 $221.35   8.748%   $240.7137   $240.71   $240.70   $240.70  
  Purchase #6 $64.90   8.561%   $70.4561   $70.46   $70.45   $70.50  
  Purchase #7 $44.63   10.265%   $49.2113   $49.21   $49.20   $49.20  
  7 purchase totals = $1,009.48       $1,114.0049   $1,114.00   $1,114.00   $1,114.10