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	$114.80	10.858%	$127.265	$127.27	$127.25	$127.30
Purchase #2	$200.91	4.233%	$209.4145	$209.41	$209.40	$209.40
Purchase #3	$51.82	6.120%	$54.9914	$54.99	$55.00	$55.00
Purchase #4	$153.70	4.175%	$160.117	$160.12	$160.10	$160.10
Purchase #5	$94.49	9.568%	$103.5308	$103.53	$103.55	$103.50
Purchase #6	$133.25	12.406%	$149.781	$149.78	$149.80	$149.80
Purchase #7	$147.69	11.622%	$164.8545	$164.85	$164.85	$164.90
7 purchase totals =	$896.66		$969.9542	$969.95	$969.95	$970.00