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	$101.38	3.398%	$104.8249	$104.82	$104.80	$104.80
Purchase #2	$217.43	3.342%	$224.6965	$224.70	$224.70	$224.70
Purchase #3	$244.50	3.827%	$253.857	$253.86	$253.85	$253.90
Purchase #4	$31.83	6.553%	$33.9158	$33.92	$33.90	$33.90
Purchase #5	$217.82	9.131%	$237.7091	$237.71	$237.70	$237.70
Purchase #6	$146.44	4.120%	$152.4733	$152.47	$152.45	$152.50
Purchase #7	$102.73	13.488%	$116.5862	$116.59	$116.60	$116.60
7 purchase totals =	$1,062.13		$1,124.0628	$1,124.07	$1,124.00	$1,124.10