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 $23.43   8.530%   $25.4286   $25.43   $25.45   $25.40  
  Purchase #2 $176.28   4.679%   $184.5281   $184.53   $184.55   $184.50  
  Purchase #3 $45.93   5.842%   $48.6132   $48.61   $48.60   $48.60  
  Purchase #4 $126.67   7.804%   $136.5553   $136.56   $136.55   $136.60  
  Purchase #5 $153.27   10.609%   $169.5304   $169.53   $169.55   $169.50  
  Purchase #6 $237.43   6.837%   $253.6631   $253.66   $253.65   $253.70  
  Purchase #7 $243.61   5.652%   $257.3788   $257.38   $257.40   $257.40  
  7 purchase totals = $1,006.62       $1,075.6975   $1,075.70   $1,075.75   $1,075.70