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	$96.86	11.605%	$108.1006	$108.10	$108.10	$108.10
Purchase #2	$74.82	9.636%	$82.0297	$82.03	$82.05	$82.00
Purchase #3	$117.87	6.710%	$125.7791	$125.78	$125.80	$125.80
Purchase #4	$14.74	5.467%	$15.5458	$15.55	$15.55	$15.50
Purchase #5	$96.85	8.462%	$105.0454	$105.05	$105.05	$105.00
Purchase #6	$164.54	4.803%	$172.4429	$172.44	$172.45	$172.40
Purchase #7	$70.72	11.167%	$78.6173	$78.62	$78.60	$78.60
7 purchase totals =	$636.40		$687.5608	$687.57	$687.60	$687.40