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	$118.76	7.727%	$127.9366	$127.94	$127.95	$127.90
Purchase #2	$133.74	9.404%	$146.3169	$146.32	$146.30	$146.30
Purchase #3	$108.38	13.534%	$123.0481	$123.05	$123.05	$123.00
Purchase #4	$224.52	6.425%	$238.9454	$238.95	$238.95	$238.90
Purchase #5	$177.49	12.666%	$199.9709	$199.97	$199.95	$200.00
Purchase #6	$154.78	11.719%	$172.9187	$172.92	$172.90	$172.90
Purchase #7	$49.84	8.462%	$54.0575	$54.06	$54.05	$54.10
7 purchase totals =	$967.51		$1,063.1941	$1,063.21	$1,063.15	$1,063.10