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 $47.86   9.561%   $52.4359   $52.44   $52.45   $52.40  
  Purchase #2 $90.93   11.141%   $101.0605   $101.06   $101.05   $101.10  
  Purchase #3 $83.49   13.255%   $94.5566   $94.56   $94.55   $94.60  
  Purchase #4 $176.78   11.645%   $197.366   $197.37   $197.35   $197.40  
  Purchase #5 $229.40   4.264%   $239.1816   $239.18   $239.20   $239.20  
  Purchase #6 $234.42   11.397%   $261.1368   $261.14   $261.15   $261.10  
  Purchase #7 $185.73   11.223%   $206.5745   $206.57   $206.55   $206.60  
  7 purchase totals = $1,048.61       $1,152.3119   $1,152.32   $1,152.30   $1,152.40