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	$124.88	4.388%	$130.3597	$130.36	$130.35	$130.40
Purchase #2	$136.49	7.233%	$146.3623	$146.36	$146.35	$146.40
Purchase #3	$131.31	4.856%	$137.6864	$137.69	$137.70	$137.70
Purchase #4	$91.59	9.816%	$100.5805	$100.58	$100.60	$100.60
Purchase #5	$5.89	9.656%	$6.4587	$6.46	$6.45	$6.50
Purchase #6	$103.28	8.501%	$112.0598	$112.06	$112.05	$112.10
Purchase #7	$248.47	9.758%	$272.7157	$272.72	$272.70	$272.70
7 purchase totals =	$841.91		$906.2231	$906.23	$906.20	$906.40