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	$197.59	4.115%	$205.7208	$205.72	$205.70	$205.70
Purchase #2	$85.35	8.246%	$92.388	$92.39	$92.40	$92.40
Purchase #3	$68.50	4.861%	$71.8298	$71.83	$71.85	$71.80
Purchase #4	$116.49	11.737%	$130.1624	$130.16	$130.15	$130.20
Purchase #5	$20.87	8.508%	$22.6456	$22.65	$22.65	$22.60
Purchase #6	$9.72	12.213%	$10.9071	$10.91	$10.90	$10.90
Purchase #7	$29.43	10.474%	$32.5125	$32.51	$32.50	$32.50
7 purchase totals =	$527.95		$566.1662	$566.17	$566.15	$566.10