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	$225.73	12.762%	$254.5377	$254.54	$254.55	$254.50
Purchase #2	$193.51	3.751%	$200.7686	$200.77	$200.75	$200.80
Purchase #3	$219.74	9.776%	$241.2218	$241.22	$241.20	$241.20
Purchase #4	$212.58	7.606%	$228.7488	$228.75	$228.75	$228.70
Purchase #5	$233.46	3.622%	$241.9159	$241.92	$241.90	$241.90
Purchase #6	$88.56	3.244%	$91.4329	$91.43	$91.45	$91.40
Purchase #7	$190.33	5.574%	$200.939	$200.94	$200.95	$200.90
7 purchase totals =	$1,363.91		$1,459.5647	$1,459.57	$1,459.55	$1,459.40