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 $62.30   13.316%   $70.5959   $70.60   $70.60   $70.60  
  Purchase #2 $47.93   9.224%   $52.3511   $52.35   $52.35   $52.40  
  Purchase #3 $195.59   12.349%   $219.7434   $219.74   $219.75   $219.70  
  Purchase #4 $46.94   11.293%   $52.2409   $52.24   $52.25   $52.20  
  Purchase #5 $130.58   3.235%   $134.8043   $134.80   $134.80   $134.80  
  Purchase #6 $48.43   7.164%   $51.8995   $51.90   $51.90   $51.90  
  Purchase #7 $130.32   3.149%   $134.4238   $134.42   $134.40   $134.40  
  7 purchase totals = $662.09       $716.0589   $716.05   $716.05   $716.00