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	$156.85	6.780%	$167.4844	$167.48	$167.50	$167.50
Purchase #2	$10.52	13.531%	$11.9435	$11.94	$11.95	$11.90
Purchase #3	$95.90	4.860%	$100.5607	$100.56	$100.55	$100.60
Purchase #4	$79.49	13.778%	$90.4421	$90.44	$90.45	$90.40
Purchase #5	$208.78	6.534%	$222.4217	$222.42	$222.40	$222.40
Purchase #6	$144.86	6.872%	$154.8148	$154.81	$154.80	$154.80
Purchase #7	$247.73	3.184%	$255.6177	$255.62	$255.60	$255.60
7 purchase totals =	$944.13		$1,003.2849	$1,003.27	$1,003.25	$1,003.20