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 $60.61   3.559%   $62.7671   $62.77   $62.75   $62.80  
  Purchase #2 $242.67   9.622%   $266.0197   $266.02   $266.00   $266.00  
  Purchase #3 $144.33   7.461%   $155.0985   $155.10   $155.10   $155.10  
  Purchase #4 $41.35   11.864%   $46.2558   $46.26   $46.25   $46.30  
  Purchase #5 $139.97   4.202%   $145.8515   $145.85   $145.85   $145.90  
  Purchase #6 $105.37   3.870%   $109.4478   $109.45   $109.45   $109.40  
  Purchase #7 $129.28   4.240%   $134.7615   $134.76   $134.75   $134.80  
  7 purchase totals = $863.58       $920.2019   $920.21   $920.15   $920.30