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	$170.83	11.815%	$191.0136	$191.01	$191.00	$191.00
Purchase #2	$132.68	7.874%	$143.1272	$143.13	$143.15	$143.10
Purchase #3	$86.55	11.699%	$96.6755	$96.68	$96.70	$96.70
Purchase #4	$111.84	10.514%	$123.5989	$123.60	$123.60	$123.60
Purchase #5	$64.72	4.422%	$67.5819	$67.58	$67.60	$67.60
Purchase #6	$113.55	8.374%	$123.0587	$123.06	$123.05	$123.10
Purchase #7	$117.97	8.257%	$127.7108	$127.71	$127.70	$127.70
7 purchase totals =	$798.14		$872.7666	$872.77	$872.80	$872.80