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	$153.34	9.870%	$168.4747	$168.47	$168.45	$168.50
Purchase #2	$209.69	9.622%	$229.8664	$229.87	$229.85	$229.90
Purchase #3	$10.63	8.121%	$11.4933	$11.49	$11.50	$11.50
Purchase #4	$75.59	9.136%	$82.4959	$82.50	$82.50	$82.50
Purchase #5	$39.90	13.553%	$45.3076	$45.31	$45.30	$45.30
Purchase #6	$189.95	10.253%	$209.4256	$209.43	$209.45	$209.40
Purchase #7	$15.89	4.522%	$16.6085	$16.61	$16.60	$16.60
7 purchase totals =	$694.99		$763.6720	$763.68	$763.65	$763.70