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	$105.61	10.433%	$116.6283	$116.63	$116.65	$116.60
Purchase #2	$223.55	4.278%	$233.1135	$233.11	$233.10	$233.10
Purchase #3	$18.45	11.138%	$20.505	$20.51	$20.50	$20.50
Purchase #4	$60.27	10.835%	$66.8003	$66.80	$66.80	$66.80
Purchase #5	$23.53	4.505%	$24.59	$24.59	$24.60	$24.60
Purchase #6	$88.86	10.725%	$98.3902	$98.39	$98.40	$98.40
Purchase #7	$114.65	4.456%	$119.7588	$119.76	$119.75	$119.80
7 purchase totals =	$634.92		$679.7861	$679.79	$679.80	$679.80