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	$194.25	4.733%	$203.4439	$203.44	$203.45	$203.40
Purchase #2	$187.58	3.108%	$193.41	$193.41	$193.40	$193.40
Purchase #3	$89.50	10.701%	$99.0774	$99.08	$99.10	$99.10
Purchase #4	$185.33	8.318%	$200.7457	$200.75	$200.75	$200.70
Purchase #5	$85.38	6.170%	$90.6479	$90.65	$90.65	$90.60
Purchase #6	$52.32	7.589%	$56.2906	$56.29	$56.30	$56.30
Purchase #7	$48.80	13.373%	$55.326	$55.33	$55.35	$55.30
7 purchase totals =	$843.16		$898.9415	$898.95	$899.00	$898.80