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 $214.47   11.604%   $239.3571   $239.36   $239.35   $239.40  
  Purchase #2 $206.52   4.369%   $215.5429   $215.54   $215.55   $215.50  
  Purchase #3 $32.67   10.574%   $36.1245   $36.12   $36.10   $36.10  
  Purchase #4 $84.99   11.332%   $94.6211   $94.62   $94.60   $94.60  
  Purchase #5 $26.69   12.132%   $29.928   $29.93   $29.95   $29.90  
  Purchase #6 $54.95   12.256%   $61.6847   $61.68   $61.70   $61.70  
  Purchase #7 $66.66   13.857%   $75.8971   $75.90   $75.90   $75.90  
  7 purchase totals = $686.95       $753.1554   $753.15   $753.15   $753.10