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	$145.76	4.446%	$152.2405	$152.24	$152.25	$152.20
Purchase #2	$213.85	9.832%	$234.8757	$234.88	$234.90	$234.90
Purchase #3	$164.54	10.291%	$181.4728	$181.47	$181.45	$181.50
Purchase #4	$246.84	12.822%	$278.4898	$278.49	$278.50	$278.50
Purchase #5	$123.45	3.707%	$128.0263	$128.03	$128.05	$128.00
Purchase #6	$89.59	12.734%	$100.9984	$101.00	$101.00	$101.00
Purchase #7	$82.29	12.526%	$92.5976	$92.60	$92.60	$92.60
7 purchase totals =	$1,066.32		$1,168.7011	$1,168.71	$1,168.75	$1,168.70