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 $185.90   4.766%   $194.76   $194.76   $194.75   $194.80  
  Purchase #2 $246.97   9.765%   $271.0866   $271.09   $271.10   $271.10  
  Purchase #3 $78.75   7.569%   $84.7106   $84.71   $84.70   $84.70  
  Purchase #4 $192.25   8.675%   $208.9277   $208.93   $208.95   $208.90  
  Purchase #5 $177.40   9.596%   $194.4233   $194.42   $194.40   $194.40  
  Purchase #6 $108.97   11.598%   $121.6083   $121.61   $121.60   $121.60  
  Purchase #7 $46.62   10.501%   $51.5156   $51.52   $51.50   $51.50  
  7 purchase totals = $1,036.86       $1,127.0321   $1,127.04   $1,127.00   $1,127.00