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	$52.40	13.662%	$59.5589	$59.56	$59.55	$59.60
Purchase #2	$243.30	4.525%	$254.3093	$254.31	$254.30	$254.30
Purchase #3	$158.92	13.496%	$180.3678	$180.37	$180.35	$180.40
Purchase #4	$213.50	11.218%	$237.4504	$237.45	$237.45	$237.50
Purchase #5	$226.82	11.325%	$252.5074	$252.51	$252.50	$252.50
Purchase #6	$32.94	12.451%	$37.0414	$37.04	$37.05	$37.00
Purchase #7	$131.80	11.281%	$146.6684	$146.67	$146.65	$146.70
7 purchase totals =	$1,059.68		$1,167.9036	$1,167.91	$1,167.85	$1,168.00