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	$41.89	10.834%	$46.4284	$46.43	$46.45	$46.40
Purchase #2	$124.56	6.202%	$132.2852	$132.29	$132.30	$132.30
Purchase #3	$183.38	11.541%	$204.5439	$204.54	$204.55	$204.50
Purchase #4	$138.87	3.673%	$143.9707	$143.97	$143.95	$144.00
Purchase #5	$243.59	13.147%	$275.6148	$275.61	$275.60	$275.60
Purchase #6	$128.83	13.736%	$146.5261	$146.53	$146.55	$146.50
Purchase #7	$181.47	11.140%	$201.6858	$201.69	$201.70	$201.70
7 purchase totals =	$1,042.59		$1,151.0549	$1,151.06	$1,151.10	$1,151.00