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	$152.83	13.541%	$173.5247	$173.52	$173.50	$173.50
Purchase #2	$10.41	9.514%	$11.4004	$11.40	$11.40	$11.40
Purchase #3	$35.96	12.174%	$40.3378	$40.34	$40.35	$40.30
Purchase #4	$77.95	10.771%	$86.346	$86.35	$86.35	$86.30
Purchase #5	$238.94	6.347%	$254.1055	$254.11	$254.10	$254.10
Purchase #6	$11.58	4.156%	$12.0613	$12.06	$12.05	$12.10
Purchase #7	$29.60	13.241%	$33.5193	$33.52	$33.50	$33.50
7 purchase totals =	$557.27		$611.2950	$611.30	$611.25	$611.20