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	$35.49	4.691%	$37.1548	$37.15	$37.15	$37.20
Purchase #2	$159.65	8.539%	$173.2825	$173.28	$173.30	$173.30
Purchase #3	$214.94	6.769%	$229.4893	$229.49	$229.50	$229.50
Purchase #4	$249.97	3.450%	$258.594	$258.59	$258.60	$258.60
Purchase #5	$76.41	3.728%	$79.2586	$79.26	$79.25	$79.30
Purchase #6	$83.81	7.182%	$89.8292	$89.83	$89.85	$89.80
Purchase #7	$53.66	13.221%	$60.7544	$60.75	$60.75	$60.80
7 purchase totals =	$873.93		$928.3628	$928.35	$928.40	$928.50