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	$132.57	6.445%	$141.1141	$141.11	$141.10	$141.10
Purchase #2	$49.86	6.408%	$53.055	$53.06	$53.05	$53.10
Purchase #3	$33.68	10.601%	$37.2504	$37.25	$37.25	$37.30
Purchase #4	$12.67	3.142%	$13.0681	$13.07	$13.05	$13.10
Purchase #5	$205.51	4.685%	$215.1381	$215.14	$215.15	$215.10
Purchase #6	$250.54	11.325%	$278.9137	$278.91	$278.90	$278.90
Purchase #7	$71.76	10.227%	$79.0989	$79.10	$79.10	$79.10
7 purchase totals =	$756.59		$817.6383	$817.64	$817.60	$817.70