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	$208.54	3.864%	$216.598	$216.60	$216.60	$216.60
Purchase #2	$200.32	7.579%	$215.5023	$215.50	$215.50	$215.50
Purchase #3	$88.81	12.344%	$99.7727	$99.77	$99.75	$99.80
Purchase #4	$52.40	5.727%	$55.4009	$55.40	$55.40	$55.40
Purchase #5	$186.80	3.195%	$192.7683	$192.77	$192.75	$192.80
Purchase #6	$139.46	3.265%	$144.0134	$144.01	$144.00	$144.00
Purchase #7	$85.72	13.280%	$97.1036	$97.10	$97.10	$97.10
7 purchase totals =	$962.05		$1,021.1592	$1,021.15	$1,021.10	$1,021.20