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	$106.32	5.562%	$112.2335	$112.23	$112.25	$112.20
Purchase #2	$76.47	3.209%	$78.9239	$78.92	$78.90	$78.90
Purchase #3	$99.36	13.182%	$112.4576	$112.46	$112.45	$112.50
Purchase #4	$111.46	4.236%	$116.1814	$116.18	$116.20	$116.20
Purchase #5	$240.62	5.143%	$252.9951	$253.00	$253.00	$253.00
Purchase #6	$127.34	13.261%	$144.2266	$144.23	$144.25	$144.20
Purchase #7	$58.75	8.673%	$63.8454	$63.85	$63.85	$63.80
7 purchase totals =	$820.32		$880.8635	$880.87	$880.90	$880.80