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	$244.54	3.396%	$252.8446	$252.84	$252.85	$252.80
Purchase #2	$96.48	9.465%	$105.6118	$105.61	$105.60	$105.60
Purchase #3	$99.32	5.736%	$105.017	$105.02	$105.00	$105.00
Purchase #4	$173.46	9.564%	$190.0497	$190.05	$190.05	$190.00
Purchase #5	$199.34	4.420%	$208.1508	$208.15	$208.15	$208.20
Purchase #6	$68.83	12.528%	$77.453	$77.45	$77.45	$77.50
Purchase #7	$158.98	3.637%	$164.7621	$164.76	$164.75	$164.80
7 purchase totals =	$1,040.95		$1,103.8890	$1,103.88	$1,103.85	$1,103.90