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	$40.40	9.794%	$44.3568	$44.36	$44.35	$44.40
Purchase #2	$204.41	10.343%	$225.5521	$225.55	$225.55	$225.60
Purchase #3	$51.41	7.726%	$55.3819	$55.38	$55.40	$55.40
Purchase #4	$44.52	4.696%	$46.6107	$46.61	$46.60	$46.60
Purchase #5	$91.72	8.729%	$99.7262	$99.73	$99.75	$99.70
Purchase #6	$117.55	11.834%	$131.4609	$131.46	$131.45	$131.50
Purchase #7	$164.70	3.177%	$169.9325	$169.93	$169.95	$169.90
7 purchase totals =	$714.71		$773.0211	$773.02	$773.05	$773.10