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	$93.37	13.797%	$106.2523	$106.25	$106.25	$106.30
Purchase #2	$29.68	3.162%	$30.6185	$30.62	$30.60	$30.60
Purchase #3	$133.75	4.805%	$140.1767	$140.18	$140.20	$140.20
Purchase #4	$99.39	12.261%	$111.5762	$111.58	$111.60	$111.60
Purchase #5	$59.74	4.779%	$62.595	$62.60	$62.60	$62.60
Purchase #6	$82.30	4.658%	$86.1335	$86.13	$86.15	$86.10
Purchase #7	$133.74	7.264%	$143.4549	$143.45	$143.45	$143.50
7 purchase totals =	$631.97		$680.8071	$680.81	$680.85	$680.90