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	$111.58	5.553%	$117.776	$117.78	$117.80	$117.80
Purchase #2	$188.84	11.249%	$210.0826	$210.08	$210.10	$210.10
Purchase #3	$142.48	13.775%	$162.1066	$162.11	$162.10	$162.10
Purchase #4	$108.85	11.706%	$121.592	$121.59	$121.60	$121.60
Purchase #5	$214.38	12.497%	$241.1711	$241.17	$241.15	$241.20
Purchase #6	$181.51	3.628%	$188.0952	$188.10	$188.10	$188.10
Purchase #7	$103.83	7.321%	$111.4314	$111.43	$111.45	$111.40
7 purchase totals =	$1,051.47		$1,152.2549	$1,152.26	$1,152.30	$1,152.30