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	$85.27	12.238%	$95.7053	$95.71	$95.70	$95.70
Purchase #2	$155.89	10.874%	$172.8415	$172.84	$172.85	$172.80
Purchase #3	$43.50	5.482%	$45.8847	$45.88	$45.90	$45.90
Purchase #4	$47.80	3.865%	$49.6475	$49.65	$49.65	$49.60
Purchase #5	$157.50	11.136%	$175.0392	$175.04	$175.05	$175.00
Purchase #6	$224.59	13.131%	$254.0809	$254.08	$254.10	$254.10
Purchase #7	$49.28	10.852%	$54.6279	$54.63	$54.65	$54.60
7 purchase totals =	$763.83		$847.8270	$847.83	$847.90	$847.70