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 $182.93   5.834%   $193.6021   $193.60   $193.60   $193.60  
  Purchase #2 $176.30   9.197%   $192.5143   $192.51   $192.50   $192.50  
  Purchase #3 $41.92   10.239%   $46.2122   $46.21   $46.20   $46.20  
  Purchase #4 $194.46   10.263%   $214.4174   $214.42   $214.40   $214.40  
  Purchase #5 $218.58   11.406%   $243.5112   $243.51   $243.50   $243.50  
  Purchase #6 $234.50   11.530%   $261.5379   $261.54   $261.55   $261.50  
  Purchase #7 $201.96   7.601%   $217.311   $217.31   $217.30   $217.30  
  7 purchase totals = $1,250.65       $1,369.1061   $1,369.10   $1,369.05   $1,369.00