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	$178.98	9.628%	$196.2122	$196.21	$196.20	$196.20
Purchase #2	$108.51	4.856%	$113.7792	$113.78	$113.80	$113.80
Purchase #3	$142.96	7.449%	$153.6091	$153.61	$153.60	$153.60
Purchase #4	$208.78	5.468%	$220.1961	$220.20	$220.20	$220.20
Purchase #5	$98.54	4.820%	$103.2896	$103.29	$103.30	$103.30
Purchase #6	$11.43	12.315%	$12.8376	$12.84	$12.85	$12.80
Purchase #7	$189.35	13.188%	$214.3215	$214.32	$214.30	$214.30
7 purchase totals =	$938.55		$1,014.2453	$1,014.25	$1,014.25	$1,014.20