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 $116.46   8.850%   $126.7667   $126.77   $126.75   $126.80  
  Purchase #2 $145.99   10.771%   $161.7146   $161.71   $161.70   $161.70  
  Purchase #3 $107.71   3.717%   $111.7136   $111.71   $111.70   $111.70  
  Purchase #4 $66.78   7.379%   $71.7077   $71.71   $71.70   $71.70  
  Purchase #5 $95.96   13.823%   $109.2246   $109.22   $109.20   $109.20  
  Purchase #6 $220.29   13.442%   $249.9014   $249.90   $249.90   $249.90  
  Purchase #7 $244.67   5.151%   $257.273   $257.27   $257.25   $257.30  
  7 purchase totals = $997.86       $1,088.3016   $1,088.29   $1,088.20   $1,088.30