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	$23.28	5.762%	$24.6214	$24.62	$24.60	$24.60
Purchase #2	$55.37	10.131%	$60.9795	$60.98	$61.00	$61.00
Purchase #3	$33.52	13.873%	$38.1702	$38.17	$38.15	$38.20
Purchase #4	$61.93	4.152%	$64.5013	$64.50	$64.50	$64.50
Purchase #5	$229.42	5.416%	$241.8454	$241.85	$241.85	$241.80
Purchase #6	$210.56	6.183%	$223.5789	$223.58	$223.60	$223.60
Purchase #7	$89.84	10.869%	$99.6047	$99.60	$99.60	$99.60
7 purchase totals =	$703.92		$753.3014	$753.30	$753.30	$753.30