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	$125.83	8.325%	$136.3053	$136.31	$136.30	$136.30
Purchase #2	$184.38	5.823%	$195.1164	$195.12	$195.10	$195.10
Purchase #3	$157.72	13.776%	$179.4475	$179.45	$179.45	$179.40
Purchase #4	$173.40	3.572%	$179.5938	$179.59	$179.60	$179.60
Purchase #5	$66.81	5.751%	$70.6522	$70.65	$70.65	$70.70
Purchase #6	$242.87	3.193%	$250.6248	$250.62	$250.60	$250.60
Purchase #7	$127.90	3.106%	$131.8726	$131.87	$131.85	$131.90
7 purchase totals =	$1,078.91		$1,143.6126	$1,143.61	$1,143.55	$1,143.60