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	$144.36	11.377%	$160.7838	$160.78	$160.80	$160.80
Purchase #2	$214.29	5.103%	$225.2252	$225.23	$225.25	$225.20
Purchase #3	$129.66	5.730%	$137.0895	$137.09	$137.10	$137.10
Purchase #4	$23.53	11.130%	$26.1489	$26.15	$26.15	$26.10
Purchase #5	$132.84	13.437%	$150.6897	$150.69	$150.70	$150.70
Purchase #6	$159.48	11.786%	$178.2763	$178.28	$178.30	$178.30
Purchase #7	$202.93	9.669%	$222.5513	$222.55	$222.55	$222.60
7 purchase totals =	$1,007.09		$1,100.7647	$1,100.77	$1,100.85	$1,100.80