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	$28.66	13.262%	$32.4609	$32.46	$32.45	$32.50
Purchase #2	$136.88	5.874%	$144.9203	$144.92	$144.90	$144.90
Purchase #3	$33.85	13.494%	$38.4177	$38.42	$38.40	$38.40
Purchase #4	$44.91	9.253%	$49.0655	$49.07	$49.05	$49.10
Purchase #5	$30.69	13.671%	$34.8856	$34.89	$34.90	$34.90
Purchase #6	$231.39	13.704%	$263.0997	$263.10	$263.10	$263.10
Purchase #7	$128.94	8.114%	$139.4022	$139.40	$139.40	$139.40
7 purchase totals =	$635.32		$702.2519	$702.26	$702.20	$702.30