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	$22.53	9.498%	$24.6699	$24.67	$24.65	$24.70
Purchase #2	$23.58	8.328%	$25.5437	$25.54	$25.55	$25.50
Purchase #3	$67.40	6.493%	$71.7763	$71.78	$71.80	$71.80
Purchase #4	$212.54	3.726%	$220.4592	$220.46	$220.45	$220.50
Purchase #5	$78.57	3.487%	$81.3097	$81.31	$81.30	$81.30
Purchase #6	$184.71	6.305%	$196.356	$196.36	$196.35	$196.40
Purchase #7	$135.76	4.189%	$141.447	$141.45	$141.45	$141.40
7 purchase totals =	$725.09		$761.5618	$761.57	$761.55	$761.60