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	$51.92	11.737%	$58.0139	$58.01	$58.00	$58.00
Purchase #2	$11.32	10.204%	$12.4751	$12.48	$12.50	$12.50
Purchase #3	$90.98	7.766%	$98.0455	$98.05	$98.05	$98.00
Purchase #4	$57.41	4.178%	$59.8086	$59.81	$59.80	$59.80
Purchase #5	$149.46	8.692%	$162.4511	$162.45	$162.45	$162.50
Purchase #6	$82.77	13.618%	$94.0416	$94.04	$94.05	$94.00
Purchase #7	$43.48	11.564%	$48.508	$48.51	$48.50	$48.50
7 purchase totals =	$487.34		$533.3438	$533.35	$533.35	$533.30