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	$45.77	13.845%	$52.1069	$52.11	$52.10	$52.10
Purchase #2	$223.93	6.546%	$238.5885	$238.59	$238.60	$238.60
Purchase #3	$11.86	4.260%	$12.3652	$12.37	$12.35	$12.40
Purchase #4	$228.26	10.505%	$252.2387	$252.24	$252.25	$252.20
Purchase #5	$29.56	9.495%	$32.3667	$32.37	$32.35	$32.40
Purchase #6	$55.30	11.157%	$61.4698	$61.47	$61.45	$61.50
Purchase #7	$59.61	7.489%	$64.0742	$64.07	$64.05	$64.10
7 purchase totals =	$654.29		$713.2100	$713.22	$713.15	$713.30