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 $233.25   4.707%   $244.2291   $244.23   $244.25   $244.20  
  Purchase #2 $128.73   11.574%   $143.6292   $143.63   $143.65   $143.60  
  Purchase #3 $183.30   6.759%   $195.6892   $195.69   $195.70   $195.70  
  Purchase #4 $77.92   5.598%   $82.282   $82.28   $82.30   $82.30  
  Purchase #5 $209.68   12.538%   $235.9697   $235.97   $235.95   $236.00  
  Purchase #6 $143.58   12.585%   $161.6495   $161.65   $161.65   $161.60  
  Purchase #7 $123.26   3.211%   $127.2179   $127.22   $127.20   $127.20  
  7 purchase totals = $1,099.72       $1,190.6666   $1,190.67   $1,190.70   $1,190.60