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	$78.60	10.474%	$86.8326	$86.83	$86.85	$86.80
Purchase #2	$211.75	13.152%	$239.5994	$239.60	$239.60	$239.60
Purchase #3	$214.82	6.562%	$228.9165	$228.92	$228.90	$228.90
Purchase #4	$65.30	13.534%	$74.1377	$74.14	$74.15	$74.10
Purchase #5	$94.91	5.139%	$99.7874	$99.79	$99.80	$99.80
Purchase #6	$94.32	9.310%	$103.1012	$103.10	$103.10	$103.10
Purchase #7	$113.50	4.757%	$118.8992	$118.90	$118.90	$118.90
7 purchase totals =	$873.20		$951.2740	$951.28	$951.30	$951.20