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 $187.87   4.342%   $196.0273   $196.03   $196.05   $196.00  
  Purchase #2 $68.79   6.569%   $73.3088   $73.31   $73.30   $73.30  
  Purchase #3 $165.69   4.584%   $173.2852   $173.29   $173.30   $173.30  
  Purchase #4 $41.51   8.172%   $44.9022   $44.90   $44.90   $44.90  
  Purchase #5 $51.30   11.845%   $57.3765   $57.38   $57.40   $57.40  
  Purchase #6 $217.96   6.531%   $232.195   $232.20   $232.20   $232.20  
  Purchase #7 $236.95   7.546%   $254.8302   $254.83   $254.85   $254.80  
  7 purchase totals = $970.07       $1,031.9252   $1,031.94   $1,032.00   $1,031.90