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	$5.57	3.565%	$5.7686	$5.77	$5.75	$5.80
Purchase #2	$36.59	6.180%	$38.8513	$38.85	$38.85	$38.90
Purchase #3	$92.47	13.161%	$104.64	$104.64	$104.65	$104.60
Purchase #4	$45.71	12.471%	$51.4105	$51.41	$51.40	$51.40
Purchase #5	$53.46	4.692%	$55.9683	$55.97	$55.95	$56.00
Purchase #6	$179.37	11.592%	$200.1626	$200.16	$200.15	$200.20
Purchase #7	$123.46	10.647%	$136.6048	$136.60	$136.60	$136.60
7 purchase totals =	$536.63		$593.4061	$593.40	$593.35	$593.50