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	$217.79	5.814%	$230.4523	$230.45	$230.45	$230.50
Purchase #2	$90.42	13.129%	$102.2912	$102.29	$102.30	$102.30
Purchase #3	$205.76	8.449%	$223.1447	$223.14	$223.15	$223.10
Purchase #4	$244.60	11.391%	$272.4624	$272.46	$272.45	$272.50
Purchase #5	$76.36	9.471%	$83.5921	$83.59	$83.60	$83.60
Purchase #6	$145.78	7.803%	$157.1552	$157.16	$157.15	$157.20
Purchase #7	$117.77	5.104%	$123.781	$123.78	$123.80	$123.80
7 purchase totals =	$1,098.48		$1,192.8789	$1,192.87	$1,192.90	$1,193.00