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	$118.67	10.834%	$131.5267	$131.53	$131.55	$131.50
Purchase #2	$16.95	3.826%	$17.5985	$17.60	$17.60	$17.60
Purchase #3	$180.92	7.123%	$193.8069	$193.81	$193.80	$193.80
Purchase #4	$74.57	5.680%	$78.8056	$78.81	$78.80	$78.80
Purchase #5	$78.53	7.459%	$84.3876	$84.39	$84.40	$84.40
Purchase #6	$181.82	3.340%	$187.8928	$187.89	$187.90	$187.90
Purchase #7	$11.27	4.300%	$11.7546	$11.75	$11.75	$11.80
7 purchase totals =	$662.73		$705.7727	$705.78	$705.80	$705.80