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	$136.85	12.128%	$153.4472	$153.45	$153.45	$153.40
Purchase #2	$57.59	6.546%	$61.3598	$61.36	$61.35	$61.40
Purchase #3	$229.67	7.699%	$247.3523	$247.35	$247.35	$247.40
Purchase #4	$32.50	13.831%	$36.9951	$37.00	$37.00	$37.00
Purchase #5	$154.32	11.677%	$172.3399	$172.34	$172.35	$172.30
Purchase #6	$160.85	4.737%	$168.4695	$168.47	$168.45	$168.50
Purchase #7	$43.50	7.288%	$46.6703	$46.67	$46.65	$46.70
7 purchase totals =	$815.28		$886.6341	$886.64	$886.60	$886.70