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	$187.29	13.669%	$212.8907	$212.89	$212.90	$212.90
Purchase #2	$138.86	11.123%	$154.3054	$154.31	$154.30	$154.30
Purchase #3	$122.31	4.385%	$127.6733	$127.67	$127.65	$127.70
Purchase #4	$71.49	11.303%	$79.5705	$79.57	$79.55	$79.60
Purchase #5	$103.67	7.346%	$111.2856	$111.29	$111.30	$111.30
Purchase #6	$154.98	4.139%	$161.3946	$161.39	$161.40	$161.40
Purchase #7	$210.67	3.268%	$217.5547	$217.55	$217.55	$217.60
7 purchase totals =	$989.27		$1,064.6748	$1,064.67	$1,064.65	$1,064.80