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	$163.89	11.182%	$182.2162	$182.22	$182.20	$182.20
Purchase #2	$131.71	11.528%	$146.8935	$146.89	$146.90	$146.90
Purchase #3	$148.39	8.781%	$161.4201	$161.42	$161.40	$161.40
Purchase #4	$72.82	8.365%	$78.9114	$78.91	$78.90	$78.90
Purchase #5	$155.94	11.308%	$173.5737	$173.57	$173.55	$173.60
Purchase #6	$226.75	9.773%	$248.9103	$248.91	$248.90	$248.90
Purchase #7	$165.94	4.298%	$173.0721	$173.07	$173.05	$173.10
7 purchase totals =	$1,065.44		$1,164.9973	$1,164.99	$1,164.90	$1,165.00