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	$218.95	13.218%	$247.8908	$247.89	$247.90	$247.90
Purchase #2	$219.67	7.149%	$235.3742	$235.37	$235.35	$235.40
Purchase #3	$139.80	10.362%	$154.2861	$154.29	$154.30	$154.30
Purchase #4	$16.39	13.621%	$18.6225	$18.62	$18.60	$18.60
Purchase #5	$126.93	4.242%	$132.3144	$132.31	$132.30	$132.30
Purchase #6	$74.97	13.821%	$85.3316	$85.33	$85.35	$85.30
Purchase #7	$131.57	6.103%	$139.5997	$139.60	$139.60	$139.60
7 purchase totals =	$928.28		$1,013.4193	$1,013.41	$1,013.40	$1,013.40