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	$238.98	10.104%	$263.1265	$263.13	$263.15	$263.10
Purchase #2	$249.68	13.409%	$283.1596	$283.16	$283.15	$283.20
Purchase #3	$150.26	10.782%	$166.461	$166.46	$166.45	$166.50
Purchase #4	$29.60	9.495%	$32.4105	$32.41	$32.40	$32.40
Purchase #5	$34.48	8.762%	$37.5011	$37.50	$37.50	$37.50
Purchase #6	$32.50	3.573%	$33.6612	$33.66	$33.65	$33.70
Purchase #7	$52.40	8.595%	$56.9038	$56.90	$56.90	$56.90
7 purchase totals =	$787.90		$873.2237	$873.22	$873.20	$873.30