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	$209.79	3.388%	$216.8977	$216.90	$216.90	$216.90
Purchase #2	$71.76	12.329%	$80.6073	$80.61	$80.60	$80.60
Purchase #3	$212.66	13.544%	$241.4627	$241.46	$241.45	$241.50
Purchase #4	$164.77	4.610%	$172.3659	$172.37	$172.35	$172.40
Purchase #5	$234.65	9.422%	$256.7587	$256.76	$256.75	$256.80
Purchase #6	$50.81	11.818%	$56.8147	$56.81	$56.80	$56.80
Purchase #7	$23.55	7.229%	$25.2524	$25.25	$25.25	$25.30
7 purchase totals =	$967.99		$1,050.1594	$1,050.16	$1,050.10	$1,050.30