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 $120.33   4.761%   $126.0589   $126.06   $126.05   $126.10  
  Purchase #2 $91.54   6.489%   $97.48   $97.48   $97.50   $97.50  
  Purchase #3 $34.27   7.134%   $36.7148   $36.71   $36.70   $36.70  
  Purchase #4 $169.53   4.340%   $176.8876   $176.89   $176.90   $176.90  
  Purchase #5 $216.29   10.812%   $239.6753   $239.68   $239.70   $239.70  
  Purchase #6 $196.62   5.867%   $208.1557   $208.16   $208.15   $208.20  
  Purchase #7 $57.39   7.832%   $61.8848   $61.88   $61.90   $61.90  
  7 purchase totals = $885.97       $946.8571   $946.86   $946.90   $947.00