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	$118.54	13.420%	$134.4481	$134.45	$134.45	$134.40
Purchase #2	$70.71	11.153%	$78.5963	$78.60	$78.60	$78.60
Purchase #3	$157.68	9.186%	$172.1645	$172.16	$172.15	$172.20
Purchase #4	$215.90	6.611%	$230.1731	$230.17	$230.15	$230.20
Purchase #5	$133.54	12.241%	$149.8866	$149.89	$149.90	$149.90
Purchase #6	$64.56	10.436%	$71.2975	$71.30	$71.30	$71.30
Purchase #7	$98.88	5.685%	$104.5013	$104.50	$104.50	$104.50
7 purchase totals =	$859.81		$941.0674	$941.07	$941.05	$941.10