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	$182.38	4.239%	$190.1111	$190.11	$190.10	$190.10
Purchase #2	$39.27	6.820%	$41.9482	$41.95	$41.95	$41.90
Purchase #3	$199.26	3.358%	$205.9512	$205.95	$205.95	$206.00
Purchase #4	$98.87	5.733%	$104.5382	$104.54	$104.55	$104.50
Purchase #5	$100.87	11.577%	$112.5477	$112.55	$112.55	$112.50
Purchase #6	$248.34	8.231%	$268.7809	$268.78	$268.80	$268.80
Purchase #7	$138.45	13.126%	$156.6229	$156.62	$156.60	$156.60
7 purchase totals =	$1,007.44		$1,080.5002	$1,080.50	$1,080.50	$1,080.40