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 $245.33   6.705%   $261.7794   $261.78   $261.80   $261.80  
  Purchase #2 $111.32   7.126%   $119.2527   $119.25   $119.25   $119.30  
  Purchase #3 $94.40   11.796%   $105.5354   $105.54   $105.55   $105.50  
  Purchase #4 $154.97   9.105%   $169.08   $169.08   $169.10   $169.10  
  Purchase #5 $187.29   11.700%   $209.2029   $209.20   $209.20   $209.20  
  Purchase #6 $217.79   5.216%   $229.1499   $229.15   $229.15   $229.10  
  Purchase #7 $206.81   6.816%   $220.9062   $220.91   $220.90   $220.90  
  7 purchase totals = $1,217.91       $1,314.9065   $1,314.91   $1,314.95   $1,314.90