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	$34.75	3.182%	$35.8557	$35.86	$35.85	$35.90
Purchase #2	$36.70	8.794%	$39.9274	$39.93	$39.95	$39.90
Purchase #3	$5.76	13.176%	$6.5189	$6.52	$6.50	$6.50
Purchase #4	$153.65	9.453%	$168.1745	$168.17	$168.15	$168.20
Purchase #5	$93.42	11.823%	$104.465	$104.47	$104.45	$104.50
Purchase #6	$100.31	5.245%	$105.5713	$105.57	$105.55	$105.60
Purchase #7	$184.54	5.388%	$194.483	$194.48	$194.50	$194.50
7 purchase totals =	$609.13		$654.9958	$655.00	$654.95	$655.10