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	$212.88	13.479%	$241.5741	$241.57	$241.55	$241.60
Purchase #2	$90.93	3.672%	$94.2689	$94.27	$94.25	$94.30
Purchase #3	$122.81	11.739%	$137.2267	$137.23	$137.25	$137.20
Purchase #4	$154.61	11.522%	$172.4242	$172.42	$172.40	$172.40
Purchase #5	$60.87	3.162%	$62.7947	$62.79	$62.80	$62.80
Purchase #6	$166.73	8.207%	$180.4135	$180.41	$180.40	$180.40
Purchase #7	$116.67	12.242%	$130.9527	$130.95	$130.95	$131.00
7 purchase totals =	$925.50		$1,019.6548	$1,019.64	$1,019.60	$1,019.70