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	$49.85	4.795%	$52.2403	$52.24	$52.25	$52.20
Purchase #2	$11.94	7.796%	$12.8708	$12.87	$12.85	$12.90
Purchase #3	$38.39	10.451%	$42.4021	$42.40	$42.40	$42.40
Purchase #4	$55.27	7.519%	$59.4258	$59.43	$59.45	$59.40
Purchase #5	$248.85	9.741%	$273.0905	$273.09	$273.10	$273.10
Purchase #6	$187.98	4.382%	$196.2173	$196.22	$196.20	$196.20
Purchase #7	$22.85	10.642%	$25.2817	$25.28	$25.30	$25.30
7 purchase totals =	$615.13		$661.5285	$661.53	$661.55	$661.50