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	$88.72	4.288%	$92.5243	$92.52	$92.50	$92.50
Purchase #2	$224.68	4.826%	$235.5231	$235.52	$235.50	$235.50
Purchase #3	$144.83	5.114%	$152.2366	$152.24	$152.25	$152.20
Purchase #4	$141.27	3.548%	$146.2823	$146.28	$146.30	$146.30
Purchase #5	$111.98	13.382%	$126.9652	$126.97	$126.95	$127.00
Purchase #6	$89.58	11.678%	$100.0412	$100.04	$100.05	$100.00
Purchase #7	$15.99	5.425%	$16.8575	$16.86	$16.85	$16.90
7 purchase totals =	$817.05		$870.4302	$870.43	$870.40	$870.40