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 $193.56   8.467%   $209.9487   $209.95   $209.95   $209.90  
  Purchase #2 $165.93   11.539%   $185.0767   $185.08   $185.10   $185.10  
  Purchase #3 $126.37   11.577%   $140.9999   $141.00   $141.00   $141.00  
  Purchase #4 $206.68   4.365%   $215.7016   $215.70   $215.70   $215.70  
  Purchase #5 $249.52   10.154%   $274.8563   $274.86   $274.85   $274.90  
  Purchase #6 $177.73   9.696%   $194.9627   $194.96   $194.95   $195.00  
  Purchase #7 $232.40   11.741%   $259.6861   $259.69   $259.70   $259.70  
  7 purchase totals = $1,352.19       $1,481.2320   $1,481.24   $1,481.25   $1,481.30