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	$139.34	3.386%	$144.0581	$144.06	$144.05	$144.10
Purchase #2	$87.51	12.669%	$98.5966	$98.60	$98.60	$98.60
Purchase #3	$232.91	12.797%	$262.7155	$262.72	$262.70	$262.70
Purchase #4	$20.33	7.760%	$21.9076	$21.91	$21.90	$21.90
Purchase #5	$100.74	10.186%	$111.0014	$111.00	$111.00	$111.00
Purchase #6	$178.59	13.731%	$203.1122	$203.11	$203.10	$203.10
Purchase #7	$219.52	5.164%	$230.856	$230.86	$230.85	$230.90
7 purchase totals =	$978.94		$1,072.2474	$1,072.26	$1,072.20	$1,072.30