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	$107.30	6.485%	$114.2584	$114.26	$114.25	$114.30
Purchase #2	$131.57	13.852%	$149.7951	$149.80	$149.80	$149.80
Purchase #3	$103.83	5.529%	$109.5708	$109.57	$109.55	$109.60
Purchase #4	$184.39	6.634%	$196.6224	$196.62	$196.60	$196.60
Purchase #5	$144.93	5.413%	$152.7751	$152.78	$152.80	$152.80
Purchase #6	$111.33	7.559%	$119.7454	$119.75	$119.75	$119.70
Purchase #7	$16.41	9.346%	$17.9437	$17.94	$17.95	$17.90
7 purchase totals =	$799.76		$860.7109	$860.72	$860.70	$860.70