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	$100.25	7.669%	$107.9382	$107.94	$107.95	$107.90
Purchase #2	$115.69	12.809%	$130.5087	$130.51	$130.50	$130.50
Purchase #3	$108.76	3.500%	$112.5666	$112.57	$112.55	$112.60
Purchase #4	$13.94	10.449%	$15.3966	$15.40	$15.40	$15.40
Purchase #5	$128.32	10.520%	$141.8193	$141.82	$141.80	$141.80
Purchase #6	$216.57	7.826%	$233.5188	$233.52	$233.50	$233.50
Purchase #7	$16.96	5.460%	$17.886	$17.89	$17.90	$17.90
7 purchase totals =	$700.49		$759.6342	$759.65	$759.60	$759.60