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	$238.44	10.846%	$264.3012	$264.30	$264.30	$264.30
Purchase #2	$84.35	4.185%	$87.88	$87.88	$87.90	$87.90
Purchase #3	$107.82	4.371%	$112.5328	$112.53	$112.55	$112.50
Purchase #4	$52.46	13.246%	$59.4089	$59.41	$59.40	$59.40
Purchase #5	$43.82	10.217%	$48.2971	$48.30	$48.30	$48.30
Purchase #6	$215.81	3.864%	$224.1489	$224.15	$224.15	$224.10
Purchase #7	$11.52	12.796%	$12.9941	$12.99	$13.00	$13.00
7 purchase totals =	$754.22		$809.5630	$809.56	$809.60	$809.50