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	$117.76	4.811%	$123.4254	$123.43	$123.45	$123.40
Purchase #2	$175.68	3.146%	$181.2069	$181.21	$181.20	$181.20
Purchase #3	$167.79	11.381%	$186.8862	$186.89	$186.90	$186.90
Purchase #4	$118.34	7.338%	$127.0238	$127.02	$127.00	$127.00
Purchase #5	$10.68	13.797%	$12.1535	$12.15	$12.15	$12.20
Purchase #6	$166.68	3.285%	$172.1554	$172.16	$172.15	$172.20
Purchase #7	$176.47	12.173%	$197.9517	$197.95	$197.95	$198.00
7 purchase totals =	$933.40		$1,000.8029	$1,000.81	$1,000.80	$1,000.90