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	$39.39	13.216%	$44.5958	$44.60	$44.60	$44.60
Purchase #2	$99.47	5.202%	$104.6444	$104.64	$104.65	$104.60
Purchase #3	$221.55	13.127%	$250.6329	$250.63	$250.65	$250.60
Purchase #4	$101.29	3.143%	$104.4735	$104.47	$104.45	$104.50
Purchase #5	$47.84	6.239%	$50.8247	$50.82	$50.80	$50.80
Purchase #6	$144.83	10.599%	$160.1805	$160.18	$160.20	$160.20
Purchase #7	$172.74	13.515%	$196.0858	$196.09	$196.10	$196.10
7 purchase totals =	$827.11		$911.4376	$911.43	$911.45	$911.40