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	$143.34	13.663%	$162.9245	$162.92	$162.90	$162.90
Purchase #2	$19.32	10.599%	$21.3677	$21.37	$21.35	$21.40
Purchase #3	$101.88	3.570%	$105.5171	$105.52	$105.50	$105.50
Purchase #4	$212.45	6.575%	$226.4186	$226.42	$226.40	$226.40
Purchase #5	$11.39	7.641%	$12.2603	$12.26	$12.25	$12.30
Purchase #6	$44.69	7.868%	$48.2062	$48.21	$48.20	$48.20
Purchase #7	$76.74	12.219%	$86.1169	$86.12	$86.10	$86.10
7 purchase totals =	$609.81		$662.8113	$662.82	$662.70	$662.80