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 $232.91   3.785%   $241.7256   $241.73   $241.75   $241.70  
  Purchase #2 $198.67   13.674%   $225.8361   $225.84   $225.85   $225.80  
  Purchase #3 $143.96   4.174%   $149.9689   $149.97   $149.95   $150.00  
  Purchase #4 $44.70   3.161%   $46.113   $46.11   $46.10   $46.10  
  Purchase #5 $195.86   10.423%   $216.2745   $216.27   $216.25   $216.30  
  Purchase #6 $205.89   13.288%   $233.2487   $233.25   $233.25   $233.20  
  Purchase #7 $210.42   6.806%   $224.7412   $224.74   $224.75   $224.70  
  7 purchase totals = $1,232.41       $1,337.9080   $1,337.91   $1,337.90   $1,337.80