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	$110.62	6.122%	$117.3922	$117.39	$117.40	$117.40
Purchase #2	$222.27	3.529%	$230.1139	$230.11	$230.10	$230.10
Purchase #3	$79.44	13.203%	$89.9285	$89.93	$89.95	$89.90
Purchase #4	$228.83	11.371%	$254.8503	$254.85	$254.85	$254.90
Purchase #5	$152.89	13.795%	$173.9812	$173.98	$174.00	$174.00
Purchase #6	$120.91	7.869%	$130.4244	$130.42	$130.40	$130.40
Purchase #7	$36.87	10.107%	$40.5965	$40.60	$40.60	$40.60
7 purchase totals =	$951.83		$1,037.2870	$1,037.28	$1,037.30	$1,037.30