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	$60.41	8.406%	$65.4881	$65.49	$65.50	$65.50
Purchase #2	$65.25	12.534%	$73.4284	$73.43	$73.45	$73.40
Purchase #3	$31.56	5.460%	$33.2832	$33.28	$33.30	$33.30
Purchase #4	$137.31	10.135%	$151.2264	$151.23	$151.25	$151.20
Purchase #5	$72.27	11.579%	$80.6381	$80.64	$80.65	$80.60
Purchase #6	$35.87	3.509%	$37.1287	$37.13	$37.15	$37.10
Purchase #7	$194.37	12.320%	$218.3164	$218.32	$218.30	$218.30
7 purchase totals =	$597.04		$659.5093	$659.52	$659.60	$659.40