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	$169.30	11.823%	$189.3163	$189.32	$189.30	$189.30
Purchase #2	$200.95	5.347%	$211.6948	$211.69	$211.70	$211.70
Purchase #3	$98.39	3.445%	$101.7795	$101.78	$101.80	$101.80
Purchase #4	$161.63	6.810%	$172.637	$172.64	$172.65	$172.60
Purchase #5	$37.85	6.102%	$40.1596	$40.16	$40.15	$40.20
Purchase #6	$101.56	12.755%	$114.514	$114.51	$114.50	$114.50
Purchase #7	$26.49	11.446%	$29.522	$29.52	$29.50	$29.50
7 purchase totals =	$796.17		$859.6232	$859.62	$859.60	$859.60