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	$226.83	8.465%	$246.0312	$246.03	$246.05	$246.00
Purchase #2	$218.70	10.407%	$241.4601	$241.46	$241.45	$241.50
Purchase #3	$217.93	9.529%	$238.6965	$238.70	$238.70	$238.70
Purchase #4	$36.76	7.849%	$39.6453	$39.65	$39.65	$39.60
Purchase #5	$6.90	12.768%	$7.781	$7.78	$7.80	$7.80
Purchase #6	$165.70	12.170%	$185.8657	$185.87	$185.85	$185.90
Purchase #7	$122.79	3.707%	$127.3418	$127.34	$127.35	$127.30
7 purchase totals =	$995.61		$1,086.8216	$1,086.83	$1,086.85	$1,086.80