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	$49.43	7.375%	$53.0755	$53.08	$53.10	$53.10
Purchase #2	$34.56	9.820%	$37.9538	$37.95	$37.95	$38.00
Purchase #3	$68.48	11.726%	$76.51	$76.51	$76.50	$76.50
Purchase #4	$212.62	8.358%	$230.3908	$230.39	$230.40	$230.40
Purchase #5	$56.55	3.644%	$58.6107	$58.61	$58.60	$58.60
Purchase #6	$139.30	11.159%	$154.8445	$154.84	$154.85	$154.80
Purchase #7	$172.69	13.800%	$196.5212	$196.52	$196.50	$196.50
7 purchase totals =	$733.63		$807.9065	$807.90	$807.90	$807.90