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	$64.41	8.152%	$69.6607	$69.66	$69.65	$69.70
Purchase #2	$103.97	8.196%	$112.4914	$112.49	$112.50	$112.50
Purchase #3	$172.56	5.551%	$182.1388	$182.14	$182.15	$182.10
Purchase #4	$25.41	10.500%	$28.0781	$28.08	$28.10	$28.10
Purchase #5	$59.49	4.367%	$62.0879	$62.09	$62.10	$62.10
Purchase #6	$40.30	5.769%	$42.6249	$42.62	$42.60	$42.60
Purchase #7	$155.25	11.248%	$172.7125	$172.71	$172.70	$172.70
7 purchase totals =	$621.39		$669.7943	$669.79	$669.80	$669.80