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	$219.48	4.828%	$230.0765	$230.08	$230.10	$230.10
Purchase #2	$78.73	4.425%	$82.2138	$82.21	$82.20	$82.20
Purchase #3	$166.69	4.321%	$173.8927	$173.89	$173.90	$173.90
Purchase #4	$237.40	6.786%	$253.51	$253.51	$253.50	$253.50
Purchase #5	$93.85	12.568%	$105.6451	$105.65	$105.65	$105.60
Purchase #6	$32.29	7.844%	$34.8228	$34.82	$34.80	$34.80
Purchase #7	$101.55	9.781%	$111.4826	$111.48	$111.50	$111.50
7 purchase totals =	$929.99		$991.6435	$991.64	$991.65	$991.60