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	$126.54	13.307%	$143.3787	$143.38	$143.40	$143.40
Purchase #2	$26.25	7.559%	$28.2342	$28.23	$28.25	$28.20
Purchase #3	$155.43	4.488%	$162.4057	$162.41	$162.40	$162.40
Purchase #4	$66.79	11.491%	$74.4648	$74.46	$74.45	$74.50
Purchase #5	$125.39	4.805%	$131.415	$131.42	$131.40	$131.40
Purchase #6	$205.44	3.461%	$212.5503	$212.55	$212.55	$212.60
Purchase #7	$98.25	13.347%	$111.3634	$111.36	$111.35	$111.40
7 purchase totals =	$804.09		$863.8121	$863.81	$863.80	$863.90