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 $95.61   8.354%   $103.5973   $103.60   $103.60   $103.60  
  Purchase #2 $151.95   9.430%   $166.2789   $166.28   $166.30   $166.30  
  Purchase #3 $102.63   7.405%   $110.2298   $110.23   $110.25   $110.20  
  Purchase #4 $72.94   11.513%   $81.3376   $81.34   $81.35   $81.30  
  Purchase #5 $53.40   5.255%   $56.2062   $56.21   $56.20   $56.20  
  Purchase #6 $116.93   3.757%   $121.3231   $121.32   $121.30   $121.30  
  Purchase #7 $110.68   11.178%   $123.0518   $123.05   $123.05   $123.10  
  7 purchase totals = $704.14       $762.0247   $762.03   $762.05   $762.00