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 $68.49   10.278%   $75.5294   $75.53   $75.55   $75.50  
  Purchase #2 $229.28   5.391%   $241.6405   $241.64   $241.65   $241.60  
  Purchase #3 $53.80   13.668%   $61.1534   $61.15   $61.15   $61.20  
  Purchase #4 $240.43   8.745%   $261.4556   $261.46   $261.45   $261.50  
  Purchase #5 $83.87   7.769%   $90.3859   $90.39   $90.40   $90.40  
  Purchase #6 $217.38   13.684%   $247.1263   $247.13   $247.15   $247.10  
  Purchase #7 $169.95   7.575%   $182.8237   $182.82   $182.80   $182.80  
  7 purchase totals = $1,063.20       $1,160.1148   $1,160.12   $1,160.15   $1,160.10