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	$214.58	6.551%	$228.6371	$228.64	$228.65	$228.60
Purchase #2	$40.35	10.793%	$44.705	$44.71	$44.70	$44.70
Purchase #3	$237.63	8.624%	$258.1232	$258.12	$258.10	$258.10
Purchase #4	$241.54	12.540%	$271.8291	$271.83	$271.85	$271.80
Purchase #5	$59.36	13.364%	$67.2929	$67.29	$67.30	$67.30
Purchase #6	$37.53	8.479%	$40.7122	$40.71	$40.70	$40.70
Purchase #7	$230.92	5.601%	$243.8538	$243.85	$243.85	$243.90
7 purchase totals =	$1,061.91		$1,155.1533	$1,155.15	$1,155.15	$1,155.10