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 $199.25   3.862%   $206.945   $206.95   $206.95   $206.90  
  Purchase #2 $56.97   5.856%   $60.3062   $60.31   $60.30   $60.30  
  Purchase #3 $237.79   9.283%   $259.864   $259.86   $259.85   $259.90  
  Purchase #4 $209.69   4.804%   $219.7635   $219.76   $219.75   $219.80  
  Purchase #5 $194.33   6.805%   $207.5542   $207.55   $207.55   $207.60  
  Purchase #6 $220.44   13.597%   $250.4132   $250.41   $250.40   $250.40  
  Purchase #7 $250.36   10.144%   $275.7565   $275.76   $275.75   $275.80  
  7 purchase totals = $1,368.83       $1,480.6026   $1,480.60   $1,480.55   $1,480.70