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	$231.92	4.547%	$242.4654	$242.47	$242.45	$242.50
Purchase #2	$42.73	13.356%	$48.437	$48.44	$48.45	$48.40
Purchase #3	$234.72	7.105%	$251.3969	$251.40	$251.40	$251.40
Purchase #4	$132.45	9.767%	$145.3864	$145.39	$145.40	$145.40
Purchase #5	$161.63	6.200%	$171.6511	$171.65	$171.65	$171.70
Purchase #6	$66.86	6.514%	$71.2153	$71.22	$71.20	$71.20
Purchase #7	$214.37	5.379%	$225.901	$225.90	$225.90	$225.90
7 purchase totals =	$1,084.68		$1,156.4531	$1,156.47	$1,156.45	$1,156.50