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	$101.93	6.705%	$108.7644	$108.76	$108.75	$108.80
Purchase #2	$138.49	4.209%	$144.319	$144.32	$144.30	$144.30
Purchase #3	$54.31	10.288%	$59.8974	$59.90	$59.90	$59.90
Purchase #4	$45.87	8.686%	$49.8543	$49.85	$49.85	$49.90
Purchase #5	$152.45	4.241%	$158.9154	$158.92	$158.90	$158.90
Purchase #6	$76.48	8.796%	$83.2072	$83.21	$83.20	$83.20
Purchase #7	$140.70	6.673%	$150.0889	$150.09	$150.10	$150.10
7 purchase totals =	$710.23		$755.0466	$755.05	$755.00	$755.10