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	$147.41	3.200%	$152.1271	$152.13	$152.15	$152.10
Purchase #2	$92.55	13.341%	$104.8971	$104.90	$104.90	$104.90
Purchase #3	$87.43	10.451%	$96.5673	$96.57	$96.55	$96.60
Purchase #4	$96.84	13.196%	$109.619	$109.62	$109.60	$109.60
Purchase #5	$138.51	9.738%	$151.9981	$152.00	$152.00	$152.00
Purchase #6	$153.40	3.707%	$159.0865	$159.09	$159.10	$159.10
Purchase #7	$222.26	7.425%	$238.7628	$238.76	$238.75	$238.80
7 purchase totals =	$938.40		$1,013.0579	$1,013.07	$1,013.05	$1,013.10