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	$196.44	3.510%	$203.335	$203.34	$203.35	$203.30
Purchase #2	$127.71	12.569%	$143.7619	$143.76	$143.75	$143.80
Purchase #3	$158.86	9.208%	$173.4878	$173.49	$173.50	$173.50
Purchase #4	$80.47	13.819%	$91.5901	$91.59	$91.60	$91.60
Purchase #5	$173.59	3.577%	$179.7993	$179.80	$179.80	$179.80
Purchase #6	$146.36	5.381%	$154.2356	$154.24	$154.25	$154.20
Purchase #7	$144.77	5.282%	$152.4168	$152.42	$152.40	$152.40
7 purchase totals =	$1,028.20		$1,098.6265	$1,098.64	$1,098.65	$1,098.60