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	$225.83	8.178%	$244.2984	$244.30	$244.30	$244.30
Purchase #2	$6.38	7.301%	$6.8458	$6.85	$6.85	$6.80
Purchase #3	$179.42	6.245%	$190.6248	$190.62	$190.60	$190.60
Purchase #4	$96.63	10.497%	$106.7733	$106.77	$106.75	$106.80
Purchase #5	$66.88	8.712%	$72.7066	$72.71	$72.70	$72.70
Purchase #6	$85.72	4.131%	$89.2611	$89.26	$89.25	$89.30
Purchase #7	$197.68	12.551%	$222.4908	$222.49	$222.50	$222.50
7 purchase totals =	$858.54		$933.0008	$933.00	$932.95	$933.00