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	$87.38	3.478%	$90.4191	$90.42	$90.40	$90.40
Purchase #2	$194.93	9.579%	$213.6023	$213.60	$213.60	$213.60
Purchase #3	$95.90	6.519%	$102.1517	$102.15	$102.15	$102.20
Purchase #4	$194.69	10.849%	$215.8119	$215.81	$215.80	$215.80
Purchase #5	$229.73	5.754%	$242.9487	$242.95	$242.95	$242.90
Purchase #6	$158.71	5.367%	$167.228	$167.23	$167.25	$167.20
Purchase #7	$28.51	10.548%	$31.5172	$31.52	$31.50	$31.50
7 purchase totals =	$989.85		$1,063.6789	$1,063.68	$1,063.65	$1,063.60