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	$146.27	12.663%	$164.7922	$164.79	$164.80	$164.80
Purchase #2	$250.60	9.633%	$274.7403	$274.74	$274.75	$274.70
Purchase #3	$138.73	9.616%	$152.0703	$152.07	$152.05	$152.10
Purchase #4	$7.44	6.714%	$7.9395	$7.94	$7.95	$7.90
Purchase #5	$51.72	4.228%	$53.9067	$53.91	$53.90	$53.90
Purchase #6	$148.32	7.258%	$159.0851	$159.09	$159.10	$159.10
Purchase #7	$244.35	4.550%	$255.4679	$255.47	$255.45	$255.50
7 purchase totals =	$987.43		$1,068.0020	$1,068.01	$1,068.00	$1,068.00