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	$6.80	6.103%	$7.215	$7.22	$7.20	$7.20
Purchase #2	$248.97	5.706%	$263.1762	$263.18	$263.20	$263.20
Purchase #3	$220.90	4.327%	$230.4583	$230.46	$230.45	$230.50
Purchase #4	$96.38	9.839%	$105.8628	$105.86	$105.85	$105.90
Purchase #5	$153.38	5.718%	$162.1503	$162.15	$162.15	$162.20
Purchase #6	$54.58	13.118%	$61.7398	$61.74	$61.75	$61.70
Purchase #7	$239.94	3.133%	$247.4573	$247.46	$247.45	$247.50
7 purchase totals =	$1,020.95		$1,078.0597	$1,078.07	$1,078.05	$1,078.20