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	$208.87	4.495%	$218.2587	$218.26	$218.25	$218.30
Purchase #2	$171.89	4.223%	$179.1489	$179.15	$179.15	$179.10
Purchase #3	$161.31	8.390%	$174.8439	$174.84	$174.85	$174.80
Purchase #4	$230.29	8.742%	$250.422	$250.42	$250.40	$250.40
Purchase #5	$213.38	9.477%	$233.602	$233.60	$233.60	$233.60
Purchase #6	$71.52	5.510%	$75.4608	$75.46	$75.45	$75.50
Purchase #7	$170.57	11.773%	$190.6512	$190.65	$190.65	$190.70
7 purchase totals =	$1,227.83		$1,322.3875	$1,322.38	$1,322.35	$1,322.40