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	$61.96	3.555%	$64.1627	$64.16	$64.15	$64.20
Purchase #2	$26.30	4.871%	$27.5811	$27.58	$27.60	$27.60
Purchase #3	$89.93	12.632%	$101.29	$101.29	$101.30	$101.30
Purchase #4	$129.96	9.769%	$142.6558	$142.66	$142.65	$142.70
Purchase #5	$245.98	3.766%	$255.2436	$255.24	$255.25	$255.20
Purchase #6	$153.54	12.698%	$173.0365	$173.04	$173.05	$173.00
Purchase #7	$117.34	8.500%	$127.3139	$127.31	$127.30	$127.30
7 purchase totals =	$825.01		$891.2836	$891.28	$891.30	$891.30