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	$51.26	13.594%	$58.2283	$58.23	$58.25	$58.20
Purchase #2	$109.25	9.384%	$119.502	$119.50	$119.50	$119.50
Purchase #3	$65.31	10.624%	$72.2485	$72.25	$72.25	$72.20
Purchase #4	$200.56	10.524%	$221.6669	$221.67	$221.65	$221.70
Purchase #5	$103.39	9.793%	$113.515	$113.52	$113.50	$113.50
Purchase #6	$84.55	5.571%	$89.2603	$89.26	$89.25	$89.30
Purchase #7	$11.99	10.126%	$13.2041	$13.20	$13.20	$13.20
7 purchase totals =	$626.31		$687.6251	$687.63	$687.60	$687.60