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	$65.77	9.799%	$72.2148	$72.21	$72.20	$72.20
Purchase #2	$78.54	4.623%	$82.1709	$82.17	$82.15	$82.20
Purchase #3	$89.91	8.612%	$97.653	$97.65	$97.65	$97.70
Purchase #4	$74.30	8.330%	$80.4892	$80.49	$80.50	$80.50
Purchase #5	$47.59	10.516%	$52.5946	$52.59	$52.60	$52.60
Purchase #6	$225.42	4.419%	$235.3813	$235.38	$235.40	$235.40
Purchase #7	$44.29	8.547%	$48.0755	$48.08	$48.10	$48.10
7 purchase totals =	$625.82		$668.5793	$668.57	$668.60	$668.70