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	$249.48	10.510%	$275.7003	$275.70	$275.70	$275.70
Purchase #2	$6.26	12.585%	$7.0478	$7.05	$7.05	$7.00
Purchase #3	$232.63	7.366%	$249.7655	$249.77	$249.75	$249.80
Purchase #4	$92.48	8.812%	$100.6293	$100.63	$100.65	$100.60
Purchase #5	$103.45	7.812%	$111.5315	$111.53	$111.55	$111.50
Purchase #6	$152.61	6.494%	$162.5205	$162.52	$162.50	$162.50
Purchase #7	$54.39	10.171%	$59.922	$59.92	$59.90	$59.90
7 purchase totals =	$891.30		$967.1169	$967.12	$967.10	$967.00