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 $191.49   11.632%   $213.7641   $213.76   $213.75   $213.80  
  Purchase #2 $131.37   11.288%   $146.199   $146.20   $146.20   $146.20  
  Purchase #3 $53.77   6.514%   $57.2726   $57.27   $57.25   $57.30  
  Purchase #4 $193.67   6.505%   $206.2682   $206.27   $206.25   $206.30  
  Purchase #5 $65.56   7.584%   $70.5321   $70.53   $70.55   $70.50  
  Purchase #6 $91.33   11.326%   $101.674   $101.67   $101.65   $101.70  
  Purchase #7 $144.87   6.825%   $154.7574   $154.76   $154.75   $154.80  
  7 purchase totals = $872.06       $950.4674   $950.46   $950.40   $950.60