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	$51.99	13.483%	$58.9998	$59.00	$59.00	$59.00
Purchase #2	$185.25	10.388%	$204.4938	$204.49	$204.50	$204.50
Purchase #3	$140.72	11.626%	$157.0801	$157.08	$157.10	$157.10
Purchase #4	$49.53	11.175%	$55.065	$55.07	$55.05	$55.10
Purchase #5	$93.39	12.863%	$105.4028	$105.40	$105.40	$105.40
Purchase #6	$88.25	7.181%	$94.5872	$94.59	$94.60	$94.60
Purchase #7	$45.42	8.219%	$49.1531	$49.15	$49.15	$49.20
7 purchase totals =	$654.55		$724.7818	$724.78	$724.80	$724.90