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	$233.32	7.776%	$251.463	$251.46	$251.45	$251.50
Purchase #2	$130.41	7.709%	$140.4633	$140.46	$140.45	$140.50
Purchase #3	$49.90	3.857%	$51.8246	$51.82	$51.80	$51.80
Purchase #4	$144.54	6.143%	$153.4191	$153.42	$153.40	$153.40
Purchase #5	$233.61	12.361%	$262.4865	$262.49	$262.50	$262.50
Purchase #6	$152.25	6.625%	$162.3366	$162.34	$162.35	$162.30
Purchase #7	$100.60	5.288%	$105.9197	$105.92	$105.90	$105.90
7 purchase totals =	$1,044.63		$1,127.9128	$1,127.91	$1,127.85	$1,127.90