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	$222.26	13.773%	$252.8719	$252.87	$252.85	$252.90
Purchase #2	$54.85	4.239%	$57.1751	$57.18	$57.20	$57.20
Purchase #3	$94.52	10.672%	$104.6072	$104.61	$104.60	$104.60
Purchase #4	$91.68	8.551%	$99.5196	$99.52	$99.50	$99.50
Purchase #5	$57.77	10.431%	$63.796	$63.80	$63.80	$63.80
Purchase #6	$211.78	6.864%	$226.3166	$226.32	$226.30	$226.30
Purchase #7	$216.96	9.800%	$238.2221	$238.22	$238.20	$238.20
7 purchase totals =	$949.82		$1,042.5085	$1,042.52	$1,042.45	$1,042.50