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	$130.49	9.493%	$142.8774	$142.88	$142.90	$142.90
Purchase #2	$205.60	5.255%	$216.4043	$216.40	$216.40	$216.40
Purchase #3	$41.50	10.430%	$45.8285	$45.83	$45.85	$45.80
Purchase #4	$223.90	7.111%	$239.8215	$239.82	$239.80	$239.80
Purchase #5	$153.57	4.640%	$160.6956	$160.70	$160.70	$160.70
Purchase #6	$215.50	4.168%	$224.482	$224.48	$224.50	$224.50
Purchase #7	$125.45	11.324%	$139.656	$139.66	$139.65	$139.70
7 purchase totals =	$1,096.01		$1,169.7653	$1,169.77	$1,169.80	$1,169.80