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	$61.25	5.471%	$64.601	$64.60	$64.60	$64.60
Purchase #2	$225.35	11.702%	$251.7205	$251.72	$251.70	$251.70
Purchase #3	$159.71	9.833%	$175.4143	$175.41	$175.40	$175.40
Purchase #4	$215.80	3.139%	$222.574	$222.57	$222.55	$222.60
Purchase #5	$97.59	13.789%	$111.0467	$111.05	$111.05	$111.00
Purchase #6	$160.33	12.678%	$180.6566	$180.66	$180.65	$180.70
Purchase #7	$48.40	3.159%	$49.929	$49.93	$49.95	$49.90
7 purchase totals =	$968.43		$1,055.9421	$1,055.94	$1,055.90	$1,055.90