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	$135.54	5.458%	$142.9378	$142.94	$142.95	$142.90
Purchase #2	$57.43	4.139%	$59.807	$59.81	$59.80	$59.80
Purchase #3	$44.98	10.677%	$49.7825	$49.78	$49.80	$49.80
Purchase #4	$66.57	6.342%	$70.7919	$70.79	$70.80	$70.80
Purchase #5	$33.30	4.636%	$34.8438	$34.84	$34.85	$34.80
Purchase #6	$166.25	13.415%	$188.5524	$188.55	$188.55	$188.60
Purchase #7	$103.38	11.848%	$115.6285	$115.63	$115.65	$115.60
7 purchase totals =	$607.45		$662.3439	$662.34	$662.40	$662.30