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 $89.47   4.670%   $93.6482   $93.65   $93.65   $93.60  
  Purchase #2 $206.29   4.120%   $214.7891   $214.79   $214.80   $214.80  
  Purchase #3 $127.36   12.788%   $143.6468   $143.65   $143.65   $143.60  
  Purchase #4 $212.59   13.259%   $240.7773   $240.78   $240.80   $240.80  
  Purchase #5 $175.86   12.749%   $198.2804   $198.28   $198.30   $198.30  
  Purchase #6 $105.76   6.733%   $112.8808   $112.88   $112.90   $112.90  
  Purchase #7 $5.67   12.751%   $6.393   $6.39   $6.40   $6.40  
  7 purchase totals = $923.00       $1,010.4156   $1,010.42   $1,010.50   $1,010.40