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	$144.32	5.207%	$151.8347	$151.83	$151.85	$151.80
Purchase #2	$109.95	8.784%	$119.608	$119.61	$119.60	$119.60
Purchase #3	$61.72	13.531%	$70.0713	$70.07	$70.05	$70.10
Purchase #4	$118.85	11.185%	$132.1434	$132.14	$132.15	$132.10
Purchase #5	$131.95	7.610%	$141.9914	$141.99	$142.00	$142.00
Purchase #6	$67.72	7.270%	$72.6432	$72.64	$72.65	$72.60
Purchase #7	$107.57	13.471%	$122.0608	$122.06	$122.05	$122.10
7 purchase totals =	$742.08		$810.3528	$810.34	$810.35	$810.30