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	$99.65	7.451%	$107.0749	$107.07	$107.05	$107.10
Purchase #2	$213.69	13.383%	$242.2881	$242.29	$242.30	$242.30
Purchase #3	$174.85	3.174%	$180.3997	$180.40	$180.40	$180.40
Purchase #4	$104.35	11.757%	$116.6184	$116.62	$116.60	$116.60
Purchase #5	$21.86	12.511%	$24.5949	$24.59	$24.60	$24.60
Purchase #6	$85.29	5.379%	$89.8777	$89.88	$89.90	$89.90
Purchase #7	$215.87	8.236%	$233.6491	$233.65	$233.65	$233.60
7 purchase totals =	$915.56		$994.5028	$994.50	$994.50	$994.50