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 $94.88   7.251%   $101.7597   $101.76   $101.75   $101.80  
  Purchase #2 $246.87   13.680%   $280.6418   $280.64   $280.65   $280.60  
  Purchase #3 $51.99   11.381%   $57.907   $57.91   $57.90   $57.90  
  Purchase #4 $50.83   10.523%   $56.1788   $56.18   $56.20   $56.20  
  Purchase #5 $223.66   7.821%   $241.1524   $241.15   $241.15   $241.20  
  Purchase #6 $226.77   8.114%   $245.1701   $245.17   $245.15   $245.20  
  Purchase #7 $53.97   13.265%   $61.1291   $61.13   $61.15   $61.10  
  7 purchase totals = $948.97       $1,043.9389   $1,043.94   $1,043.95   $1,044.00