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	$163.42	5.741%	$172.8019	$172.80	$172.80	$172.80
Purchase #2	$171.90	3.752%	$178.3497	$178.35	$178.35	$178.30
Purchase #3	$249.31	9.373%	$272.6778	$272.68	$272.70	$272.70
Purchase #4	$143.63	13.421%	$162.9066	$162.91	$162.90	$162.90
Purchase #5	$72.78	4.484%	$76.0435	$76.04	$76.05	$76.00
Purchase #6	$173.31	13.638%	$196.946	$196.95	$196.95	$196.90
Purchase #7	$162.35	6.320%	$172.6105	$172.61	$172.60	$172.60
7 purchase totals =	$1,136.70		$1,232.3360	$1,232.34	$1,232.35	$1,232.20