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	$100.26	3.128%	$103.3961	$103.40	$103.40	$103.40
Purchase #2	$7.73	5.725%	$8.1725	$8.17	$8.15	$8.20
Purchase #3	$24.62	9.707%	$27.0099	$27.01	$27.00	$27.00
Purchase #4	$35.72	5.564%	$37.7075	$37.71	$37.70	$37.70
Purchase #5	$207.60	5.399%	$218.8083	$218.81	$218.80	$218.80
Purchase #6	$151.65	4.124%	$157.904	$157.90	$157.90	$157.90
Purchase #7	$139.76	12.247%	$156.8764	$156.88	$156.90	$156.90
7 purchase totals =	$667.34		$709.8747	$709.88	$709.85	$709.90