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	$36.91	10.683%	$40.8531	$40.85	$40.85	$40.90
Purchase #2	$136.64	11.444%	$152.2771	$152.28	$152.30	$152.30
Purchase #3	$214.80	6.382%	$228.5085	$228.51	$228.50	$228.50
Purchase #4	$150.48	10.186%	$165.8079	$165.81	$165.80	$165.80
Purchase #5	$154.52	12.704%	$174.1502	$174.15	$174.15	$174.20
Purchase #6	$185.40	5.545%	$195.6804	$195.68	$195.70	$195.70
Purchase #7	$204.65	11.476%	$228.1356	$228.14	$228.15	$228.10
7 purchase totals =	$1,083.40		$1,185.4128	$1,185.42	$1,185.45	$1,185.50