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	$178.58	12.211%	$200.3864	$200.39	$200.40	$200.40
Purchase #2	$41.37	5.457%	$43.6276	$43.63	$43.65	$43.60
Purchase #3	$108.51	7.801%	$116.9749	$116.97	$116.95	$117.00
Purchase #4	$136.82	10.769%	$151.5541	$151.55	$151.55	$151.60
Purchase #5	$87.60	13.200%	$99.1632	$99.16	$99.15	$99.20
Purchase #6	$246.73	12.328%	$277.1469	$277.15	$277.15	$277.10
Purchase #7	$167.68	5.217%	$176.4279	$176.43	$176.45	$176.40
7 purchase totals =	$967.29		$1,065.2810	$1,065.28	$1,065.30	$1,065.30