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	$70.79	7.771%	$76.2911	$76.29	$76.30	$76.30
Purchase #2	$13.51	9.682%	$14.818	$14.82	$14.80	$14.80
Purchase #3	$173.95	13.186%	$196.887	$196.89	$196.90	$196.90
Purchase #4	$169.32	12.348%	$190.2276	$190.23	$190.25	$190.20
Purchase #5	$141.65	5.704%	$149.7297	$149.73	$149.75	$149.70
Purchase #6	$102.60	3.288%	$105.9735	$105.97	$105.95	$106.00
Purchase #7	$122.56	4.800%	$128.4429	$128.44	$128.45	$128.40
7 purchase totals =	$794.38		$862.3698	$862.37	$862.40	$862.30