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	$63.45	7.658%	$68.309	$68.31	$68.30	$68.30
Purchase #2	$172.37	8.770%	$187.4868	$187.49	$187.50	$187.50
Purchase #3	$102.60	7.161%	$109.9472	$109.95	$109.95	$109.90
Purchase #4	$179.45	4.501%	$187.527	$187.53	$187.55	$187.50
Purchase #5	$73.40	12.701%	$82.7225	$82.72	$82.70	$82.70
Purchase #6	$55.89	8.258%	$60.5054	$60.51	$60.50	$60.50
Purchase #7	$29.46	11.270%	$32.7801	$32.78	$32.80	$32.80
7 purchase totals =	$676.62		$729.2780	$729.29	$729.30	$729.20