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	$237.67	6.233%	$252.484	$252.48	$252.50	$252.50
Purchase #2	$117.60	8.205%	$127.2491	$127.25	$127.25	$127.20
Purchase #3	$192.44	10.376%	$212.4076	$212.41	$212.40	$212.40
Purchase #4	$231.67	10.106%	$255.0826	$255.08	$255.10	$255.10
Purchase #5	$110.51	5.276%	$116.3405	$116.34	$116.35	$116.30
Purchase #6	$199.67	12.843%	$225.3136	$225.31	$225.30	$225.30
Purchase #7	$190.39	4.831%	$199.5877	$199.59	$199.60	$199.60
7 purchase totals =	$1,279.95		$1,388.4651	$1,388.46	$1,388.50	$1,388.40