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	$116.33	10.741%	$128.825	$128.83	$128.85	$128.80
Purchase #2	$97.83	11.258%	$108.8437	$108.84	$108.85	$108.80
Purchase #3	$52.70	9.679%	$57.8008	$57.80	$57.80	$57.80
Purchase #4	$123.77	3.249%	$127.7913	$127.79	$127.80	$127.80
Purchase #5	$145.52	5.747%	$153.883	$153.88	$153.90	$153.90
Purchase #6	$139.86	3.155%	$144.2726	$144.27	$144.25	$144.30
Purchase #7	$66.66	13.647%	$75.7571	$75.76	$75.75	$75.80
7 purchase totals =	$742.67		$797.1735	$797.17	$797.20	$797.20