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	$91.88	11.286%	$102.2496	$102.25	$102.25	$102.20
Purchase #2	$122.60	12.668%	$138.131	$138.13	$138.15	$138.10
Purchase #3	$228.34	4.821%	$239.3483	$239.35	$239.35	$239.30
Purchase #4	$228.94	10.732%	$253.5098	$253.51	$253.50	$253.50
Purchase #5	$178.50	6.491%	$190.0864	$190.09	$190.10	$190.10
Purchase #6	$114.80	7.215%	$123.0828	$123.08	$123.10	$123.10
Purchase #7	$94.28	5.114%	$99.1015	$99.10	$99.10	$99.10
7 purchase totals =	$1,059.34		$1,145.5094	$1,145.51	$1,145.55	$1,145.40