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	$129.49	12.826%	$146.0984	$146.10	$146.10	$146.10
Purchase #2	$110.75	11.565%	$123.5582	$123.56	$123.55	$123.60
Purchase #3	$237.33	10.630%	$262.5582	$262.56	$262.55	$262.60
Purchase #4	$37.56	3.150%	$38.7431	$38.74	$38.75	$38.70
Purchase #5	$77.27	13.363%	$87.5956	$87.60	$87.60	$87.60
Purchase #6	$190.42	5.244%	$200.4056	$200.41	$200.40	$200.40
Purchase #7	$173.39	3.622%	$179.6702	$179.67	$179.65	$179.70
7 purchase totals =	$956.21		$1,038.6293	$1,038.64	$1,038.60	$1,038.70