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	$91.89	12.504%	$103.3799	$103.38	$103.40	$103.40
Purchase #2	$142.35	12.202%	$159.7195	$159.72	$159.70	$159.70
Purchase #3	$51.30	3.813%	$53.2561	$53.26	$53.25	$53.30
Purchase #4	$105.87	5.515%	$111.7087	$111.71	$111.70	$111.70
Purchase #5	$60.63	3.199%	$62.5696	$62.57	$62.55	$62.60
Purchase #6	$159.28	13.840%	$181.3244	$181.32	$181.30	$181.30
Purchase #7	$21.28	10.398%	$23.4927	$23.49	$23.50	$23.50
7 purchase totals =	$632.60		$695.4509	$695.45	$695.40	$695.50