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	$132.47	9.832%	$145.4945	$145.49	$145.50	$145.50
Purchase #2	$180.68	8.692%	$196.3847	$196.38	$196.40	$196.40
Purchase #3	$29.57	5.816%	$31.2898	$31.29	$31.30	$31.30
Purchase #4	$235.39	8.421%	$255.2122	$255.21	$255.20	$255.20
Purchase #5	$166.94	11.576%	$186.265	$186.27	$186.25	$186.30
Purchase #6	$31.79	12.143%	$35.6503	$35.65	$35.65	$35.70
Purchase #7	$190.68	7.295%	$204.5901	$204.59	$204.60	$204.60
7 purchase totals =	$967.52		$1,054.8866	$1,054.88	$1,054.90	$1,055.00