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	$69.77	5.803%	$73.8188	$73.82	$73.80	$73.80
Purchase #2	$14.62	5.502%	$15.4244	$15.42	$15.40	$15.40
Purchase #3	$69.67	12.680%	$78.5042	$78.50	$78.50	$78.50
Purchase #4	$7.45	11.608%	$8.3148	$8.31	$8.30	$8.30
Purchase #5	$54.55	8.452%	$59.1606	$59.16	$59.15	$59.20
Purchase #6	$101.35	10.604%	$112.0972	$112.10	$112.10	$112.10
Purchase #7	$211.74	11.337%	$235.745	$235.75	$235.75	$235.70
7 purchase totals =	$529.15		$583.0650	$583.06	$583.00	$583.00