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 $13.64   4.376%   $14.2369   $14.24   $14.25   $14.20  
  Purchase #2 $155.25   10.233%   $171.1367   $171.14   $171.15   $171.10  
  Purchase #3 $160.44   9.338%   $175.4219   $175.42   $175.40   $175.40  
  Purchase #4 $210.94   4.485%   $220.4007   $220.40   $220.40   $220.40  
  Purchase #5 $96.87   5.253%   $101.9586   $101.96   $101.95   $102.00  
  Purchase #6 $20.67   9.335%   $22.5995   $22.60   $22.60   $22.60  
  Purchase #7 $38.52   9.798%   $42.2942   $42.29   $42.30   $42.30  
  7 purchase totals = $696.33       $748.0485   $748.05   $748.05   $748.00