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	$22.95	13.604%	$26.0721	$26.07	$26.05	$26.10
Purchase #2	$79.49	12.647%	$89.5431	$89.54	$89.55	$89.50
Purchase #3	$174.92	3.445%	$180.946	$180.95	$180.95	$180.90
Purchase #4	$34.58	8.108%	$37.3837	$37.38	$37.40	$37.40
Purchase #5	$235.55	9.558%	$258.0639	$258.06	$258.05	$258.10
Purchase #6	$156.77	6.462%	$166.9005	$166.90	$166.90	$166.90
Purchase #7	$20.40	6.487%	$21.7233	$21.72	$21.70	$21.70
7 purchase totals =	$724.66		$780.6326	$780.62	$780.60	$780.60