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 $23.92   10.138%   $26.345   $26.35   $26.35   $26.30  
  Purchase #2 $195.40   13.421%   $221.6246   $221.62   $221.60   $221.60  
  Purchase #3 $153.65   13.437%   $174.296   $174.30   $174.30   $174.30  
  Purchase #4 $197.78   8.507%   $214.6051   $214.61   $214.60   $214.60  
  Purchase #5 $229.54   7.824%   $247.4992   $247.50   $247.50   $247.50  
  Purchase #6 $56.83   9.570%   $62.2686   $62.27   $62.25   $62.30  
  Purchase #7 $102.56   12.501%   $115.381   $115.38   $115.40   $115.40  
  7 purchase totals = $959.68       $1,062.0195   $1,062.03   $1,062.00   $1,062.00