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	$104.50	6.723%	$111.5255	$111.53	$111.55	$111.50
Purchase #2	$37.50	11.603%	$41.8511	$41.85	$41.85	$41.90
Purchase #3	$23.86	3.399%	$24.671	$24.67	$24.65	$24.70
Purchase #4	$220.77	7.827%	$238.0497	$238.05	$238.05	$238.00
Purchase #5	$216.32	7.193%	$231.8799	$231.88	$231.90	$231.90
Purchase #6	$153.30	13.168%	$173.4865	$173.49	$173.50	$173.50
Purchase #7	$246.27	7.773%	$265.4126	$265.41	$265.40	$265.40
7 purchase totals =	$1,002.52		$1,086.8763	$1,086.88	$1,086.90	$1,086.90