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 $207.98   3.542%   $215.3467   $215.35   $215.35   $215.30  
  Purchase #2 $130.31   4.613%   $136.3212   $136.32   $136.30   $136.30  
  Purchase #3 $222.79   9.738%   $244.4853   $244.49   $244.50   $244.50  
  Purchase #4 $104.62   13.701%   $118.954   $118.95   $118.95   $119.00  
  Purchase #5 $39.58   5.150%   $41.6184   $41.62   $41.60   $41.60  
  Purchase #6 $178.55   8.111%   $193.0322   $193.03   $193.05   $193.00  
  Purchase #7 $243.42   7.631%   $261.9954   $262.00   $262.00   $262.00  
  7 purchase totals = $1,127.25       $1,211.7532   $1,211.76   $1,211.75   $1,211.70