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 $210.36   3.460%   $217.6385   $217.64   $217.65   $217.60  
  Purchase #2 $212.30   13.660%   $241.3002   $241.30   $241.30   $241.30  
  Purchase #3 $95.70   8.145%   $103.4948   $103.49   $103.50   $103.50  
  Purchase #4 $130.78   6.532%   $139.3225   $139.32   $139.30   $139.30  
  Purchase #5 $15.59   5.779%   $16.4909   $16.49   $16.50   $16.50  
  Purchase #6 $189.82   8.502%   $205.9585   $205.96   $205.95   $206.00  
  Purchase #7 $113.73   7.538%   $122.303   $122.30   $122.30   $122.30  
  7 purchase totals = $968.28       $1,046.5084   $1,046.50   $1,046.50   $1,046.50