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	$45.31	9.302%	$49.5247	$49.52	$49.50	$49.50
Purchase #2	$12.55	9.245%	$13.7102	$13.71	$13.70	$13.70
Purchase #3	$69.25	13.490%	$78.5918	$78.59	$78.60	$78.60
Purchase #4	$18.87	6.239%	$20.0473	$20.05	$20.05	$20.00
Purchase #5	$27.67	12.644%	$31.1686	$31.17	$31.15	$31.20
Purchase #6	$237.33	7.816%	$255.8797	$255.88	$255.90	$255.90
Purchase #7	$18.68	5.836%	$19.7702	$19.77	$19.75	$19.80
7 purchase totals =	$429.66		$468.6925	$468.69	$468.65	$468.70