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	$216.72	6.358%	$230.4991	$230.50	$230.50	$230.50
Purchase #2	$153.65	12.337%	$172.6058	$172.61	$172.60	$172.60
Purchase #3	$247.72	6.784%	$264.5253	$264.53	$264.55	$264.50
Purchase #4	$158.85	11.194%	$176.6317	$176.63	$176.65	$176.60
Purchase #5	$83.38	10.782%	$92.37	$92.37	$92.35	$92.40
Purchase #6	$71.57	9.303%	$78.2282	$78.23	$78.25	$78.20
Purchase #7	$95.57	6.346%	$101.6349	$101.63	$101.65	$101.60
7 purchase totals =	$1,027.46		$1,116.4950	$1,116.50	$1,116.55	$1,116.40