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	$225.85	4.245%	$235.4373	$235.44	$235.45	$235.40
Purchase #2	$72.91	5.510%	$76.9273	$76.93	$76.95	$76.90
Purchase #3	$76.30	8.417%	$82.7222	$82.72	$82.70	$82.70
Purchase #4	$56.78	13.847%	$64.6423	$64.64	$64.65	$64.60
Purchase #5	$197.64	6.297%	$210.0854	$210.09	$210.10	$210.10
Purchase #6	$101.87	9.132%	$111.1728	$111.17	$111.15	$111.20
Purchase #7	$192.79	13.451%	$218.7222	$218.72	$218.70	$218.70
7 purchase totals =	$924.14		$999.7095	$999.71	$999.70	$999.60