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	$100.58	4.520%	$105.1262	$105.13	$105.15	$105.10
Purchase #2	$52.92	8.335%	$57.3309	$57.33	$57.35	$57.30
Purchase #3	$19.50	10.601%	$21.5672	$21.57	$21.55	$21.60
Purchase #4	$206.31	11.868%	$230.7949	$230.79	$230.80	$230.80
Purchase #5	$54.74	13.620%	$62.1956	$62.20	$62.20	$62.20
Purchase #6	$70.71	10.810%	$78.3538	$78.35	$78.35	$78.40
Purchase #7	$131.45	13.461%	$149.1445	$149.14	$149.15	$149.10
7 purchase totals =	$636.21		$704.5131	$704.51	$704.55	$704.50