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	$191.40	12.232%	$214.812	$214.81	$214.80	$214.80
Purchase #2	$108.45	6.435%	$115.4288	$115.43	$115.45	$115.40
Purchase #3	$136.86	3.671%	$141.8841	$141.88	$141.90	$141.90
Purchase #4	$197.87	11.638%	$220.8981	$220.90	$220.90	$220.90
Purchase #5	$40.77	3.825%	$42.3295	$42.33	$42.35	$42.30
Purchase #6	$155.78	11.589%	$173.8333	$173.83	$173.85	$173.80
Purchase #7	$36.32	4.451%	$37.9366	$37.94	$37.95	$37.90
7 purchase totals =	$867.45		$947.1224	$947.12	$947.20	$947.00