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	$38.77	10.271%	$42.7521	$42.75	$42.75	$42.80
Purchase #2	$156.42	12.798%	$176.4386	$176.44	$176.45	$176.40
Purchase #3	$237.98	5.849%	$251.8995	$251.90	$251.90	$251.90
Purchase #4	$193.94	4.469%	$202.6072	$202.61	$202.60	$202.60
Purchase #5	$99.91	11.734%	$111.6334	$111.63	$111.65	$111.60
Purchase #6	$199.54	9.522%	$218.5402	$218.54	$218.55	$218.50
Purchase #7	$140.83	4.781%	$147.5631	$147.56	$147.55	$147.60
7 purchase totals =	$1,067.39		$1,151.4341	$1,151.43	$1,151.45	$1,151.40