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	$119.86	12.569%	$134.9252	$134.93	$134.95	$134.90
Purchase #2	$17.73	10.254%	$19.548	$19.55	$19.55	$19.50
Purchase #3	$131.83	11.426%	$146.8929	$146.89	$146.90	$146.90
Purchase #4	$75.43	4.374%	$78.7293	$78.73	$78.75	$78.70
Purchase #5	$13.35	13.538%	$15.1573	$15.16	$15.15	$15.20
Purchase #6	$167.43	7.212%	$179.5051	$179.51	$179.50	$179.50
Purchase #7	$64.25	5.816%	$67.9868	$67.99	$68.00	$68.00
7 purchase totals =	$589.88		$642.7446	$642.76	$642.80	$642.70