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	$230.72	6.408%	$245.5045	$245.50	$245.50	$245.50
Purchase #2	$38.47	7.532%	$41.3676	$41.37	$41.35	$41.40
Purchase #3	$43.42	13.273%	$49.1831	$49.18	$49.20	$49.20
Purchase #4	$133.93	13.382%	$151.8525	$151.85	$151.85	$151.90
Purchase #5	$249.33	13.676%	$283.4284	$283.43	$283.45	$283.40
Purchase #6	$69.87	6.642%	$74.5108	$74.51	$74.50	$74.50
Purchase #7	$156.78	3.710%	$162.5965	$162.60	$162.60	$162.60
7 purchase totals =	$922.52		$1,008.4434	$1,008.44	$1,008.45	$1,008.50