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	$243.45	4.724%	$254.9506	$254.95	$254.95	$255.00
Purchase #2	$229.51	5.307%	$241.6901	$241.69	$241.70	$241.70
Purchase #3	$127.73	4.608%	$133.6158	$133.62	$133.60	$133.60
Purchase #4	$17.91	3.631%	$18.5603	$18.56	$18.55	$18.60
Purchase #5	$190.80	4.376%	$199.1494	$199.15	$199.15	$199.10
Purchase #6	$20.82	7.660%	$22.4148	$22.41	$22.40	$22.40
Purchase #7	$190.53	13.135%	$215.5561	$215.56	$215.55	$215.60
7 purchase totals =	$1,020.75		$1,085.9371	$1,085.94	$1,085.90	$1,086.00