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	$177.82	7.298%	$190.7973	$190.80	$190.80	$190.80
Purchase #2	$172.52	4.700%	$180.6284	$180.63	$180.65	$180.60
Purchase #3	$112.49	3.338%	$116.2449	$116.24	$116.25	$116.20
Purchase #4	$40.68	6.500%	$43.3242	$43.32	$43.30	$43.30
Purchase #5	$96.28	9.342%	$105.2745	$105.27	$105.25	$105.30
Purchase #6	$132.44	9.317%	$144.7794	$144.78	$144.80	$144.80
Purchase #7	$109.53	3.576%	$113.4468	$113.45	$113.45	$113.40
7 purchase totals =	$841.76		$894.4955	$894.49	$894.50	$894.40