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	$163.54	9.327%	$178.7934	$178.79	$178.80	$178.80
Purchase #2	$76.73	4.555%	$80.2251	$80.23	$80.25	$80.20
Purchase #3	$72.36	8.423%	$78.4549	$78.45	$78.45	$78.50
Purchase #4	$210.85	6.500%	$224.5553	$224.56	$224.55	$224.60
Purchase #5	$141.93	11.865%	$158.77	$158.77	$158.75	$158.80
Purchase #6	$119.94	10.729%	$132.8084	$132.81	$132.80	$132.80
Purchase #7	$101.60	9.547%	$111.2998	$111.30	$111.30	$111.30
7 purchase totals =	$886.95		$964.9069	$964.91	$964.90	$965.00