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	$202.59	9.394%	$221.6213	$221.62	$221.60	$221.60
Purchase #2	$192.90	4.171%	$200.9459	$200.95	$200.95	$200.90
Purchase #3	$180.45	5.501%	$190.3766	$190.38	$190.40	$190.40
Purchase #4	$246.46	7.577%	$265.1343	$265.13	$265.15	$265.10
Purchase #5	$118.87	13.326%	$134.7106	$134.71	$134.70	$134.70
Purchase #6	$103.64	8.315%	$112.2577	$112.26	$112.25	$112.30
Purchase #7	$78.75	8.710%	$85.6091	$85.61	$85.60	$85.60
7 purchase totals =	$1,123.66		$1,210.6555	$1,210.66	$1,210.65	$1,210.60