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	$133.86	6.600%	$142.6948	$142.69	$142.70	$142.70
Purchase #2	$19.88	3.182%	$20.5126	$20.51	$20.50	$20.50
Purchase #3	$127.90	3.599%	$132.5031	$132.50	$132.50	$132.50
Purchase #4	$116.87	7.679%	$125.8444	$125.84	$125.85	$125.80
Purchase #5	$158.37	10.259%	$174.6172	$174.62	$174.60	$174.60
Purchase #6	$89.44	10.326%	$98.6756	$98.68	$98.70	$98.70
Purchase #7	$107.47	3.339%	$111.0584	$111.06	$111.05	$111.10
7 purchase totals =	$753.79		$805.9061	$805.90	$805.90	$805.90