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	$43.60	13.209%	$49.3591	$49.36	$49.35	$49.40
Purchase #2	$194.69	10.222%	$214.5912	$214.59	$214.60	$214.60
Purchase #3	$140.61	6.829%	$150.2123	$150.21	$150.20	$150.20
Purchase #4	$41.43	9.689%	$45.4442	$45.44	$45.45	$45.40
Purchase #5	$150.61	12.523%	$169.4709	$169.47	$169.45	$169.50
Purchase #6	$106.50	4.704%	$111.5098	$111.51	$111.50	$111.50
Purchase #7	$145.84	7.193%	$156.3303	$156.33	$156.35	$156.30
7 purchase totals =	$823.28		$896.9178	$896.91	$896.90	$896.90