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	$57.70	8.396%	$62.5445	$62.54	$62.55	$62.50
Purchase #2	$199.29	12.234%	$223.6711	$223.67	$223.65	$223.70
Purchase #3	$161.79	7.457%	$173.8547	$173.85	$173.85	$173.90
Purchase #4	$110.45	5.142%	$116.1293	$116.13	$116.15	$116.10
Purchase #5	$57.64	12.764%	$64.9972	$65.00	$65.00	$65.00
Purchase #6	$5.62	11.660%	$6.2753	$6.28	$6.30	$6.30
Purchase #7	$82.92	9.505%	$90.8015	$90.80	$90.80	$90.80
7 purchase totals =	$675.41		$738.2736	$738.27	$738.30	$738.30