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	$116.59	9.494%	$127.6591	$127.66	$127.65	$127.70
Purchase #2	$22.98	8.235%	$24.8724	$24.87	$24.85	$24.90
Purchase #3	$233.27	13.307%	$264.3112	$264.31	$264.30	$264.30
Purchase #4	$175.83	13.644%	$199.8202	$199.82	$199.80	$199.80
Purchase #5	$50.73	13.506%	$57.5816	$57.58	$57.60	$57.60
Purchase #6	$160.28	8.763%	$174.3253	$174.33	$174.35	$174.30
Purchase #7	$34.42	9.115%	$37.5574	$37.56	$37.55	$37.60
7 purchase totals =	$794.10		$886.1272	$886.13	$886.10	$886.20