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	$46.35	8.651%	$50.3597	$50.36	$50.35	$50.40
Purchase #2	$61.66	8.670%	$67.0059	$67.01	$67.00	$67.00
Purchase #3	$13.76	13.362%	$15.5986	$15.60	$15.60	$15.60
Purchase #4	$199.92	8.139%	$216.1915	$216.19	$216.20	$216.20
Purchase #5	$88.77	12.842%	$100.1698	$100.17	$100.15	$100.20
Purchase #6	$214.32	12.379%	$240.8507	$240.85	$240.85	$240.90
Purchase #7	$104.29	12.549%	$117.3774	$117.38	$117.40	$117.40
7 purchase totals =	$729.07		$807.5536	$807.56	$807.55	$807.70