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	$230.28	11.235%	$256.152	$256.15	$256.15	$256.20
Purchase #2	$247.42	12.342%	$277.9566	$277.96	$277.95	$278.00
Purchase #3	$51.76	3.227%	$53.4303	$53.43	$53.45	$53.40
Purchase #4	$130.88	7.439%	$140.6162	$140.62	$140.60	$140.60
Purchase #5	$124.33	10.519%	$137.4083	$137.41	$137.40	$137.40
Purchase #6	$89.77	12.441%	$100.9383	$100.94	$100.95	$100.90
Purchase #7	$101.28	6.419%	$107.7812	$107.78	$107.80	$107.80
7 purchase totals =	$975.72		$1,074.2829	$1,074.29	$1,074.30	$1,074.30