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	$214.41	13.282%	$242.8879	$242.89	$242.90	$242.90
Purchase #2	$215.77	8.717%	$234.5787	$234.58	$234.60	$234.60
Purchase #3	$48.27	10.839%	$53.502	$53.50	$53.50	$53.50
Purchase #4	$77.93	10.776%	$86.3277	$86.33	$86.35	$86.30
Purchase #5	$49.38	5.411%	$52.052	$52.05	$52.05	$52.10
Purchase #6	$203.61	4.532%	$212.8376	$212.84	$212.85	$212.80
Purchase #7	$106.27	5.277%	$111.8779	$111.88	$111.90	$111.90
7 purchase totals =	$915.64		$994.0638	$994.07	$994.15	$994.10