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	$185.72	7.746%	$200.1059	$200.11	$200.10	$200.10
Purchase #2	$230.54	4.294%	$240.4394	$240.44	$240.45	$240.40
Purchase #3	$52.28	9.280%	$57.1316	$57.13	$57.15	$57.10
Purchase #4	$45.43	11.560%	$50.6817	$50.68	$50.70	$50.70
Purchase #5	$140.50	9.169%	$153.3824	$153.38	$153.40	$153.40
Purchase #6	$146.66	8.509%	$159.1393	$159.14	$159.15	$159.10
Purchase #7	$210.65	3.153%	$217.2918	$217.29	$217.30	$217.30
7 purchase totals =	$1,011.78		$1,078.1721	$1,078.17	$1,078.25	$1,078.10