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	$97.80	10.255%	$107.8294	$107.83	$107.85	$107.80
Purchase #2	$83.72	6.480%	$89.1451	$89.15	$89.15	$89.10
Purchase #3	$78.47	9.350%	$85.8069	$85.81	$85.80	$85.80
Purchase #4	$197.81	3.209%	$204.1577	$204.16	$204.15	$204.20
Purchase #5	$231.46	9.131%	$252.5946	$252.59	$252.60	$252.60
Purchase #6	$12.75	11.616%	$14.231	$14.23	$14.25	$14.20
Purchase #7	$195.46	13.851%	$222.5332	$222.53	$222.55	$222.50
7 purchase totals =	$897.47		$976.2979	$976.30	$976.35	$976.20