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	$134.77	8.261%	$145.9033	$145.90	$145.90	$145.90
Purchase #2	$142.43	5.418%	$150.1469	$150.15	$150.15	$150.10
Purchase #3	$221.40	7.131%	$237.188	$237.19	$237.20	$237.20
Purchase #4	$12.52	4.449%	$13.077	$13.08	$13.10	$13.10
Purchase #5	$78.61	6.232%	$83.509	$83.51	$83.50	$83.50
Purchase #6	$107.35	3.822%	$111.4529	$111.45	$111.45	$111.50
Purchase #7	$126.64	6.510%	$134.8843	$134.88	$134.90	$134.90
7 purchase totals =	$823.72		$876.1614	$876.16	$876.20	$876.20