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	$99.60	5.436%	$105.0143	$105.01	$105.00	$105.00
Purchase #2	$144.78	6.351%	$153.975	$153.98	$154.00	$154.00
Purchase #3	$213.69	13.300%	$242.1108	$242.11	$242.10	$242.10
Purchase #4	$60.63	8.168%	$65.5823	$65.58	$65.60	$65.60
Purchase #5	$57.41	11.765%	$64.1643	$64.16	$64.15	$64.20
Purchase #6	$169.48	8.458%	$183.8146	$183.81	$183.80	$183.80
Purchase #7	$164.45	4.694%	$172.1693	$172.17	$172.15	$172.20
7 purchase totals =	$910.04		$986.8306	$986.82	$986.80	$986.90