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 $58.69   11.438%   $65.403   $65.40   $65.40   $65.40  
  Purchase #2 $148.73   13.250%   $168.4367   $168.44   $168.45   $168.40  
  Purchase #3 $123.68   7.845%   $133.3827   $133.38   $133.40   $133.40  
  Purchase #4 $206.30   3.802%   $214.1435   $214.14   $214.15   $214.10  
  Purchase #5 $169.53   3.176%   $174.9143   $174.91   $174.90   $174.90  
  Purchase #6 $191.29   11.623%   $213.5236   $213.52   $213.50   $213.50  
  Purchase #7 $81.43   13.755%   $92.6307   $92.63   $92.65   $92.60  
  7 purchase totals = $979.65       $1,062.4345   $1,062.42   $1,062.45   $1,062.30