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	$142.94	6.388%	$152.071	$152.07	$152.05	$152.10
Purchase #2	$83.77	9.779%	$91.9619	$91.96	$91.95	$92.00
Purchase #3	$142.38	4.328%	$148.5422	$148.54	$148.55	$148.50
Purchase #4	$60.29	3.289%	$62.2729	$62.27	$62.25	$62.30
Purchase #5	$105.87	5.211%	$111.3869	$111.39	$111.40	$111.40
Purchase #6	$18.52	10.221%	$20.4129	$20.41	$20.40	$20.40
Purchase #7	$182.73	3.380%	$188.9063	$188.91	$188.90	$188.90
7 purchase totals =	$736.50		$775.5541	$775.55	$775.50	$775.60