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	$123.88	8.219%	$134.0617	$134.06	$134.05	$134.10
Purchase #2	$90.78	9.362%	$99.2788	$99.28	$99.30	$99.30
Purchase #3	$54.78	12.247%	$61.4889	$61.49	$61.50	$61.50
Purchase #4	$126.96	13.414%	$143.9904	$143.99	$144.00	$144.00
Purchase #5	$174.85	9.523%	$191.501	$191.50	$191.50	$191.50
Purchase #6	$40.83	13.651%	$46.4037	$46.40	$46.40	$46.40
Purchase #7	$185.87	11.411%	$207.0796	$207.08	$207.10	$207.10
7 purchase totals =	$797.95		$883.8041	$883.80	$883.85	$883.90