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	$195.27	9.396%	$213.6176	$213.62	$213.60	$213.60
Purchase #2	$68.92	5.124%	$72.4515	$72.45	$72.45	$72.50
Purchase #3	$189.78	3.378%	$196.1908	$196.19	$196.20	$196.20
Purchase #4	$125.28	10.831%	$138.8491	$138.85	$138.85	$138.80
Purchase #5	$87.37	13.807%	$99.4332	$99.43	$99.45	$99.40
Purchase #6	$185.63	11.821%	$207.5733	$207.57	$207.55	$207.60
Purchase #7	$53.83	4.439%	$56.2195	$56.22	$56.20	$56.20
7 purchase totals =	$906.08		$984.3350	$984.33	$984.30	$984.30