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 $37.44   9.660%   $41.0567   $41.06   $41.05   $41.10  
  Purchase #2 $110.28   8.222%   $119.3472   $119.35   $119.35   $119.30  
  Purchase #3 $247.91   13.531%   $281.4547   $281.45   $281.45   $281.50  
  Purchase #4 $223.70   4.103%   $232.8784   $232.88   $232.90   $232.90  
  Purchase #5 $33.44   6.726%   $35.6892   $35.69   $35.70   $35.70  
  Purchase #6 $170.69   4.142%   $177.76   $177.76   $177.75   $177.80  
  Purchase #7 $250.80   11.627%   $279.9605   $279.96   $279.95   $280.00  
  7 purchase totals = $1,074.26       $1,168.1467   $1,168.15   $1,168.15   $1,168.30