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	$62.38	4.670%	$65.2931	$65.29	$65.30	$65.30
Purchase #2	$104.45	11.621%	$116.5881	$116.59	$116.60	$116.60
Purchase #3	$26.85	12.700%	$30.26	$30.26	$30.25	$30.30
Purchase #4	$43.25	7.219%	$46.3722	$46.37	$46.35	$46.40
Purchase #5	$33.86	10.659%	$37.4691	$37.47	$37.45	$37.50
Purchase #6	$195.79	4.338%	$204.2834	$204.28	$204.30	$204.30
Purchase #7	$186.58	7.324%	$200.2451	$200.25	$200.25	$200.20
7 purchase totals =	$653.16		$700.5110	$700.51	$700.50	$700.60