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	$223.26	4.290%	$232.8379	$232.84	$232.85	$232.80
Purchase #2	$99.28	13.245%	$112.4296	$112.43	$112.45	$112.40
Purchase #3	$37.38	7.683%	$40.2519	$40.25	$40.25	$40.30
Purchase #4	$203.72	12.137%	$228.4455	$228.45	$228.45	$228.40
Purchase #5	$39.63	9.644%	$43.4519	$43.45	$43.45	$43.50
Purchase #6	$151.72	4.151%	$158.0179	$158.02	$158.00	$158.00
Purchase #7	$169.37	12.657%	$190.8072	$190.81	$190.80	$190.80
7 purchase totals =	$924.36		$1,006.2419	$1,006.25	$1,006.25	$1,006.20