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	$119.75	10.560%	$132.3956	$132.40	$132.40	$132.40
Purchase #2	$96.51	8.633%	$104.8417	$104.84	$104.85	$104.80
Purchase #3	$116.72	8.430%	$126.5595	$126.56	$126.55	$126.60
Purchase #4	$42.58	9.831%	$46.766	$46.77	$46.75	$46.80
Purchase #5	$103.50	5.785%	$109.4875	$109.49	$109.50	$109.50
Purchase #6	$230.60	10.336%	$254.4348	$254.43	$254.45	$254.40
Purchase #7	$91.56	9.220%	$100.0018	$100.00	$100.00	$100.00
7 purchase totals =	$801.22		$874.4869	$874.49	$874.50	$874.50