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	$154.84	11.255%	$172.2672	$172.27	$172.25	$172.30
Purchase #2	$147.37	5.323%	$155.2145	$155.21	$155.20	$155.20
Purchase #3	$98.30	4.446%	$102.6704	$102.67	$102.65	$102.70
Purchase #4	$146.91	3.345%	$151.8241	$151.82	$151.80	$151.80
Purchase #5	$202.42	4.648%	$211.8285	$211.83	$211.85	$211.80
Purchase #6	$127.39	7.248%	$136.6232	$136.62	$136.60	$136.60
Purchase #7	$200.82	11.447%	$223.8079	$223.81	$223.80	$223.80
7 purchase totals =	$1,078.05		$1,154.2358	$1,154.23	$1,154.15	$1,154.20