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	$203.39	6.839%	$217.2998	$217.30	$217.30	$217.30
Purchase #2	$151.47	4.175%	$157.7939	$157.79	$157.80	$157.80
Purchase #3	$217.95	11.540%	$243.1014	$243.10	$243.10	$243.10
Purchase #4	$121.58	7.675%	$130.9113	$130.91	$130.90	$130.90
Purchase #5	$105.70	12.410%	$118.8174	$118.82	$118.80	$118.80
Purchase #6	$134.54	4.682%	$140.8392	$140.84	$140.85	$140.80
Purchase #7	$168.60	11.304%	$187.6585	$187.66	$187.65	$187.70
7 purchase totals =	$1,103.23		$1,196.4215	$1,196.42	$1,196.40	$1,196.40