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	$71.82	8.784%	$78.1287	$78.13	$78.15	$78.10
Purchase #2	$57.29	4.777%	$60.0267	$60.03	$60.05	$60.00
Purchase #3	$12.53	4.788%	$13.1299	$13.13	$13.15	$13.10
Purchase #4	$60.69	9.114%	$66.2213	$66.22	$66.20	$66.20
Purchase #5	$99.97	12.437%	$112.4033	$112.40	$112.40	$112.40
Purchase #6	$18.36	12.734%	$20.698	$20.70	$20.70	$20.70
Purchase #7	$32.61	3.787%	$33.8449	$33.84	$33.85	$33.80
7 purchase totals =	$353.27		$384.4528	$384.45	$384.50	$384.30