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 $244.80   7.128%   $262.2493   $262.25   $262.25   $262.20  
  Purchase #2 $13.81   9.755%   $15.1572   $15.16   $15.15   $15.20  
  Purchase #3 $247.34   8.671%   $268.7869   $268.79   $268.80   $268.80  
  Purchase #4 $233.50   4.540%   $244.1009   $244.10   $244.10   $244.10  
  Purchase #5 $12.49   11.594%   $13.9381   $13.94   $13.95   $13.90  
  Purchase #6 $218.29   13.662%   $248.1128   $248.11   $248.10   $248.10  
  Purchase #7 $174.94   4.389%   $182.6181   $182.62   $182.60   $182.60  
  7 purchase totals = $1,145.17       $1,234.9633   $1,234.97   $1,234.95   $1,234.90