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	$173.60	9.595%	$190.2569	$190.26	$190.25	$190.30
Purchase #2	$242.46	7.421%	$260.453	$260.45	$260.45	$260.50
Purchase #3	$65.49	8.806%	$71.257	$71.26	$71.25	$71.30
Purchase #4	$122.81	13.700%	$139.635	$139.64	$139.65	$139.60
Purchase #5	$154.80	4.396%	$161.605	$161.61	$161.60	$161.60
Purchase #6	$85.81	4.772%	$89.9049	$89.90	$89.90	$89.90
Purchase #7	$246.80	11.509%	$275.2042	$275.20	$275.20	$275.20
7 purchase totals =	$1,091.77		$1,188.3160	$1,188.32	$1,188.30	$1,188.40