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	$250.62	8.868%	$272.845	$272.85	$272.85	$272.80
Purchase #2	$20.82	8.163%	$22.5195	$22.52	$22.50	$22.50
Purchase #3	$146.58	6.521%	$156.1385	$156.14	$156.15	$156.10
Purchase #4	$29.70	4.736%	$31.1066	$31.11	$31.10	$31.10
Purchase #5	$153.90	9.712%	$168.8468	$168.85	$168.85	$168.80
Purchase #6	$32.33	8.162%	$34.9688	$34.97	$34.95	$35.00
Purchase #7	$112.47	3.271%	$116.1489	$116.15	$116.15	$116.10
7 purchase totals =	$746.42		$802.5741	$802.59	$802.55	$802.40