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	$250.83	9.259%	$274.0543	$274.05	$274.05	$274.10
Purchase #2	$209.85	4.498%	$219.2891	$219.29	$219.30	$219.30
Purchase #3	$238.89	7.202%	$256.0949	$256.09	$256.10	$256.10
Purchase #4	$19.60	6.359%	$20.8464	$20.85	$20.85	$20.80
Purchase #5	$230.39	10.776%	$255.2168	$255.22	$255.20	$255.20
Purchase #6	$102.88	6.323%	$109.3851	$109.39	$109.40	$109.40
Purchase #7	$234.69	11.326%	$261.271	$261.27	$261.25	$261.30
7 purchase totals =	$1,287.13		$1,396.1576	$1,396.16	$1,396.15	$1,396.20