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	$65.25	11.591%	$72.8131	$72.81	$72.80	$72.80
Purchase #2	$175.40	9.569%	$192.184	$192.18	$192.20	$192.20
Purchase #3	$138.27	4.569%	$144.5876	$144.59	$144.60	$144.60
Purchase #4	$176.69	7.460%	$189.8711	$189.87	$189.85	$189.90
Purchase #5	$56.80	7.652%	$61.1463	$61.15	$61.15	$61.10
Purchase #6	$106.98	12.225%	$120.0583	$120.06	$120.05	$120.10
Purchase #7	$238.96	12.397%	$268.5839	$268.58	$268.60	$268.60
7 purchase totals =	$958.35		$1,049.2443	$1,049.24	$1,049.25	$1,049.30