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 $94.75   3.374%   $97.9469   $97.95   $97.95   $97.90  
  Purchase #2 $173.42   11.722%   $193.7483   $193.75   $193.75   $193.70  
  Purchase #3 $171.98   10.554%   $190.1308   $190.13   $190.15   $190.10  
  Purchase #4 $126.44   11.722%   $141.2613   $141.26   $141.25   $141.30  
  Purchase #5 $184.36   13.732%   $209.6763   $209.68   $209.70   $209.70  
  Purchase #6 $161.26   11.699%   $180.1258   $180.13   $180.15   $180.10  
  Purchase #7 $218.55   8.563%   $237.2644   $237.26   $237.25   $237.30  
  7 purchase totals = $1,130.76       $1,250.1538   $1,250.16   $1,250.20   $1,250.10