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	$96.80	5.347%	$101.9759	$101.98	$102.00	$102.00
Purchase #2	$241.90	7.665%	$260.4416	$260.44	$260.45	$260.40
Purchase #3	$42.80	9.281%	$46.7723	$46.77	$46.75	$46.80
Purchase #4	$98.66	13.161%	$111.6446	$111.64	$111.65	$111.60
Purchase #5	$59.25	10.685%	$65.5809	$65.58	$65.60	$65.60
Purchase #6	$102.28	5.209%	$107.6078	$107.61	$107.60	$107.60
Purchase #7	$241.58	11.563%	$269.5139	$269.51	$269.50	$269.50
7 purchase totals =	$883.27		$963.5370	$963.53	$963.55	$963.50