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	$209.28	8.660%	$227.4036	$227.40	$227.40	$227.40
Purchase #2	$129.53	7.776%	$139.6023	$139.60	$139.60	$139.60
Purchase #3	$174.46	12.854%	$196.8851	$196.89	$196.90	$196.90
Purchase #4	$173.54	10.334%	$191.4736	$191.47	$191.45	$191.50
Purchase #5	$7.92	11.253%	$8.8112	$8.81	$8.80	$8.80
Purchase #6	$228.66	4.828%	$239.6997	$239.70	$239.70	$239.70
Purchase #7	$39.32	13.479%	$44.6199	$44.62	$44.60	$44.60
7 purchase totals =	$962.71		$1,048.4954	$1,048.49	$1,048.45	$1,048.50