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	$159.53	8.675%	$173.3692	$173.37	$173.35	$173.40
Purchase #2	$232.89	8.273%	$252.157	$252.16	$252.15	$252.20
Purchase #3	$109.51	7.308%	$117.513	$117.51	$117.50	$117.50
Purchase #4	$150.32	10.382%	$165.9262	$165.93	$165.95	$165.90
Purchase #5	$201.45	6.145%	$213.8291	$213.83	$213.85	$213.80
Purchase #6	$210.97	5.360%	$222.278	$222.28	$222.30	$222.30
Purchase #7	$131.86	7.321%	$141.5135	$141.51	$141.50	$141.50
7 purchase totals =	$1,196.53		$1,286.5860	$1,286.59	$1,286.60	$1,286.60