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	$35.55	8.310%	$38.5042	$38.50	$38.50	$38.50
Purchase #2	$30.60	3.586%	$31.6973	$31.70	$31.70	$31.70
Purchase #3	$59.42	13.402%	$67.3835	$67.38	$67.40	$67.40
Purchase #4	$49.85	6.628%	$53.1541	$53.15	$53.15	$53.20
Purchase #5	$190.56	3.176%	$196.6122	$196.61	$196.60	$196.60
Purchase #6	$213.86	12.310%	$240.1862	$240.19	$240.20	$240.20
Purchase #7	$172.88	12.720%	$194.8703	$194.87	$194.85	$194.90
7 purchase totals =	$752.72		$822.4078	$822.40	$822.40	$822.50