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 $45.76   11.387%   $50.9707   $50.97   $50.95   $51.00  
  Purchase #2 $185.70   5.750%   $196.3778   $196.38   $196.40   $196.40  
  Purchase #3 $241.77   6.627%   $257.7921   $257.79   $257.80   $257.80  
  Purchase #4 $49.64   7.155%   $53.1917   $53.19   $53.20   $53.20  
  Purchase #5 $88.71   7.828%   $95.6542   $95.65   $95.65   $95.70  
  Purchase #6 $239.26   9.781%   $262.662   $262.66   $262.65   $262.70  
  Purchase #7 $168.29   12.408%   $189.1714   $189.17   $189.15   $189.20  
  7 purchase totals = $1,019.13       $1,105.8199   $1,105.81   $1,105.80   $1,106.00