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	$157.87	9.726%	$173.2244	$173.22	$173.20	$173.20
Purchase #2	$156.89	9.154%	$171.2517	$171.25	$171.25	$171.30
Purchase #3	$114.54	13.482%	$129.9823	$129.98	$130.00	$130.00
Purchase #4	$241.40	8.259%	$261.3372	$261.34	$261.35	$261.30
Purchase #5	$111.74	13.764%	$127.1199	$127.12	$127.10	$127.10
Purchase #6	$34.87	9.451%	$38.1656	$38.17	$38.15	$38.20
Purchase #7	$59.85	7.628%	$64.4154	$64.42	$64.40	$64.40
7 purchase totals =	$877.16		$965.4965	$965.50	$965.45	$965.50