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	$129.38	12.821%	$145.9678	$145.97	$145.95	$146.00
Purchase #2	$31.67	3.194%	$32.6815	$32.68	$32.70	$32.70
Purchase #3	$172.31	10.790%	$190.9022	$190.90	$190.90	$190.90
Purchase #4	$72.37	13.723%	$82.3013	$82.30	$82.30	$82.30
Purchase #5	$217.72	13.128%	$246.3023	$246.30	$246.30	$246.30
Purchase #6	$118.54	7.462%	$127.3855	$127.39	$127.40	$127.40
Purchase #7	$222.64	3.432%	$230.281	$230.28	$230.30	$230.30
7 purchase totals =	$964.63		$1,055.8216	$1,055.82	$1,055.85	$1,055.90