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	$199.41	7.856%	$215.0756	$215.08	$215.10	$215.10
Purchase #2	$46.87	4.115%	$48.7987	$48.80	$48.80	$48.80
Purchase #3	$191.81	9.205%	$209.4661	$209.47	$209.45	$209.50
Purchase #4	$111.45	7.146%	$119.4142	$119.41	$119.40	$119.40
Purchase #5	$66.67	8.138%	$72.0956	$72.10	$72.10	$72.10
Purchase #6	$132.62	9.510%	$145.2322	$145.23	$145.25	$145.20
Purchase #7	$66.50	7.411%	$71.4283	$71.43	$71.45	$71.40
7 purchase totals =	$815.33		$881.5107	$881.52	$881.55	$881.50