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	$215.38	7.614%	$231.779	$231.78	$231.80	$231.80
Purchase #2	$71.77	6.846%	$76.6834	$76.68	$76.70	$76.70
Purchase #3	$74.47	4.548%	$77.8569	$77.86	$77.85	$77.90
Purchase #4	$5.78	11.526%	$6.4462	$6.45	$6.45	$6.40
Purchase #5	$27.62	3.512%	$28.59	$28.59	$28.60	$28.60
Purchase #6	$240.52	4.159%	$250.5232	$250.52	$250.50	$250.50
Purchase #7	$84.25	6.736%	$89.9251	$89.93	$89.95	$89.90
7 purchase totals =	$719.79		$761.8038	$761.81	$761.85	$761.80