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	$110.25	5.509%	$116.3237	$116.32	$116.30	$116.30
Purchase #2	$247.80	7.584%	$266.5932	$266.59	$266.60	$266.60
Purchase #3	$85.31	4.532%	$89.1762	$89.18	$89.20	$89.20
Purchase #4	$151.85	5.431%	$160.097	$160.10	$160.10	$160.10
Purchase #5	$95.82	4.520%	$100.1511	$100.15	$100.15	$100.20
Purchase #6	$167.94	6.434%	$178.7453	$178.75	$178.75	$178.70
Purchase #7	$227.83	5.147%	$239.5564	$239.56	$239.55	$239.60
7 purchase totals =	$1,086.80		$1,150.6429	$1,150.65	$1,150.65	$1,150.70