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	$213.80	9.389%	$233.8737	$233.87	$233.85	$233.90
Purchase #2	$24.83	12.407%	$27.9107	$27.91	$27.90	$27.90
Purchase #3	$16.60	10.235%	$18.299	$18.30	$18.30	$18.30
Purchase #4	$145.71	9.807%	$159.9998	$160.00	$160.00	$160.00
Purchase #5	$188.86	6.169%	$200.5108	$200.51	$200.50	$200.50
Purchase #6	$84.25	6.109%	$89.3968	$89.40	$89.40	$89.40
Purchase #7	$123.91	11.260%	$137.8623	$137.86	$137.85	$137.90
7 purchase totals =	$797.96		$867.8531	$867.85	$867.80	$867.90