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	$154.88	13.648%	$176.018	$176.02	$176.00	$176.00
Purchase #2	$89.49	12.466%	$100.6458	$100.65	$100.65	$100.60
Purchase #3	$162.25	5.786%	$171.6378	$171.64	$171.65	$171.60
Purchase #4	$18.73	4.664%	$19.6036	$19.60	$19.60	$19.60
Purchase #5	$59.77	7.870%	$64.4739	$64.47	$64.45	$64.50
Purchase #6	$50.80	11.739%	$56.7634	$56.76	$56.75	$56.80
Purchase #7	$117.38	3.242%	$121.1855	$121.19	$121.20	$121.20
7 purchase totals =	$653.30		$710.3280	$710.33	$710.30	$710.30