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	$157.42	13.534%	$178.7252	$178.73	$178.75	$178.70
Purchase #2	$105.74	13.645%	$120.1682	$120.17	$120.15	$120.20
Purchase #3	$89.44	13.787%	$101.7711	$101.77	$101.75	$101.80
Purchase #4	$185.96	3.537%	$192.5374	$192.54	$192.55	$192.50
Purchase #5	$51.83	9.298%	$56.6492	$56.65	$56.65	$56.60
Purchase #6	$143.59	5.566%	$151.5822	$151.58	$151.60	$151.60
Purchase #7	$184.29	6.492%	$196.2541	$196.25	$196.25	$196.30
7 purchase totals =	$918.27		$997.6874	$997.69	$997.70	$997.70