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	$230.65	4.148%	$240.2174	$240.22	$240.20	$240.20
Purchase #2	$138.52	10.633%	$153.2488	$153.25	$153.25	$153.20
Purchase #3	$155.44	7.838%	$167.6234	$167.62	$167.60	$167.60
Purchase #4	$157.90	13.308%	$178.9133	$178.91	$178.90	$178.90
Purchase #5	$35.52	11.407%	$39.5718	$39.57	$39.55	$39.60
Purchase #6	$130.60	11.576%	$145.7183	$145.72	$145.70	$145.70
Purchase #7	$154.44	11.439%	$172.1064	$172.11	$172.10	$172.10
7 purchase totals =	$1,003.07		$1,097.3994	$1,097.40	$1,097.30	$1,097.30