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 $175.63   11.587%   $195.9802   $195.98   $196.00   $196.00  
  Purchase #2 $238.30   7.359%   $255.8365   $255.84   $255.85   $255.80  
  Purchase #3 $84.66   11.223%   $94.1614   $94.16   $94.15   $94.20  
  Purchase #4 $244.27   9.417%   $267.2729   $267.27   $267.25   $267.30  
  Purchase #5 $242.46   9.717%   $266.0198   $266.02   $266.00   $266.00  
  Purchase #6 $114.34   8.138%   $123.645   $123.65   $123.65   $123.60  
  Purchase #7 $157.46   5.511%   $166.1376   $166.14   $166.15   $166.10  
  7 purchase totals = $1,257.12       $1,369.0534   $1,369.06   $1,369.05   $1,369.00