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	$184.52	8.844%	$200.8389	$200.84	$200.85	$200.80
Purchase #2	$112.49	13.624%	$127.8156	$127.82	$127.80	$127.80
Purchase #3	$27.51	3.123%	$28.3691	$28.37	$28.35	$28.40
Purchase #4	$77.66	4.841%	$81.4195	$81.42	$81.40	$81.40
Purchase #5	$51.72	3.457%	$53.508	$53.51	$53.50	$53.50
Purchase #6	$230.90	9.220%	$252.189	$252.19	$252.20	$252.20
Purchase #7	$133.53	13.556%	$151.6313	$151.63	$151.65	$151.60
7 purchase totals =	$818.33		$895.7714	$895.78	$895.75	$895.70