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	$200.54	6.692%	$213.9601	$213.96	$213.95	$214.00
Purchase #2	$153.68	7.255%	$164.8295	$164.83	$164.85	$164.80
Purchase #3	$130.32	8.843%	$141.8442	$141.84	$141.85	$141.80
Purchase #4	$145.98	5.774%	$154.4089	$154.41	$154.40	$154.40
Purchase #5	$88.34	12.384%	$99.28	$99.28	$99.30	$99.30
Purchase #6	$38.54	4.408%	$40.2388	$40.24	$40.25	$40.20
Purchase #7	$183.48	3.558%	$190.0082	$190.01	$190.00	$190.00
7 purchase totals =	$940.88		$1,004.5697	$1,004.57	$1,004.60	$1,004.50