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	$91.46	7.308%	$98.1439	$98.14	$98.15	$98.10
Purchase #2	$185.27	7.114%	$198.4501	$198.45	$198.45	$198.50
Purchase #3	$41.71	8.619%	$45.305	$45.31	$45.30	$45.30
Purchase #4	$95.47	9.668%	$104.7	$104.70	$104.70	$104.70
Purchase #5	$215.41	10.703%	$238.4653	$238.47	$238.45	$238.50
Purchase #6	$181.89	5.343%	$191.6084	$191.61	$191.60	$191.60
Purchase #7	$59.91	6.733%	$63.9437	$63.94	$63.95	$63.90
7 purchase totals =	$871.12		$940.6164	$940.62	$940.60	$940.60