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	$176.29	13.699%	$200.44	$200.44	$200.45	$200.40
Purchase #2	$194.33	13.447%	$220.4616	$220.46	$220.45	$220.50
Purchase #3	$11.34	10.624%	$12.5448	$12.54	$12.55	$12.50
Purchase #4	$94.90	11.327%	$105.6493	$105.65	$105.65	$105.60
Purchase #5	$234.33	4.304%	$244.4156	$244.42	$244.40	$244.40
Purchase #6	$143.61	6.371%	$152.7594	$152.76	$152.75	$152.80
Purchase #7	$47.64	12.380%	$53.5378	$53.54	$53.55	$53.50
7 purchase totals =	$902.44		$989.8085	$989.81	$989.80	$989.70