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	$19.81	3.870%	$20.5766	$20.58	$20.60	$20.60
Purchase #2	$83.37	4.192%	$86.8649	$86.86	$86.85	$86.90
Purchase #3	$101.77	4.290%	$106.1359	$106.14	$106.15	$106.10
Purchase #4	$210.52	5.201%	$221.4691	$221.47	$221.45	$221.50
Purchase #5	$100.94	8.151%	$109.1676	$109.17	$109.15	$109.20
Purchase #6	$233.83	3.463%	$241.9275	$241.93	$241.95	$241.90
Purchase #7	$206.63	11.421%	$230.2292	$230.23	$230.25	$230.20
7 purchase totals =	$956.87		$1,016.3708	$1,016.38	$1,016.40	$1,016.40