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 $60.60   7.207%   $64.9674   $64.97   $64.95   $65.00  
  Purchase #2 $106.88   5.537%   $112.7979   $112.80   $112.80   $112.80  
  Purchase #3 $75.38   5.247%   $79.3352   $79.34   $79.35   $79.30  
  Purchase #4 $114.93   6.621%   $122.5395   $122.54   $122.55   $122.50  
  Purchase #5 $228.95   3.242%   $236.3726   $236.37   $236.35   $236.40  
  Purchase #6 $165.26   13.206%   $187.0842   $187.08   $187.10   $187.10  
  Purchase #7 $116.47   6.526%   $124.0708   $124.07   $124.05   $124.10  
  7 purchase totals = $868.47       $927.1676   $927.17   $927.15   $927.20