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	$112.89	12.620%	$127.1367	$127.14	$127.15	$127.10
Purchase #2	$64.45	8.678%	$70.043	$70.04	$70.05	$70.00
Purchase #3	$199.46	11.224%	$221.8474	$221.85	$221.85	$221.80
Purchase #4	$40.60	11.721%	$45.3587	$45.36	$45.35	$45.40
Purchase #5	$246.69	11.793%	$275.7822	$275.78	$275.80	$275.80
Purchase #6	$220.36	13.698%	$250.5449	$250.54	$250.55	$250.50
Purchase #7	$93.80	10.492%	$103.6415	$103.64	$103.65	$103.60
7 purchase totals =	$978.25		$1,094.3544	$1,094.35	$1,094.40	$1,094.20