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 $214.44   12.549%   $241.3501   $241.35   $241.35   $241.40  
  Purchase #2 $9.82   3.725%   $10.1858   $10.19   $10.20   $10.20  
  Purchase #3 $171.37   12.403%   $192.625   $192.63   $192.65   $192.60  
  Purchase #4 $137.92   10.736%   $152.7271   $152.73   $152.75   $152.70  
  Purchase #5 $71.70   3.530%   $74.231   $74.23   $74.25   $74.20  
  Purchase #6 $118.79   3.776%   $123.2755   $123.28   $123.30   $123.30  
  Purchase #7 $90.26   12.173%   $101.2473   $101.25   $101.25   $101.20  
  7 purchase totals = $814.30       $895.6418   $895.66   $895.75   $895.60