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	$95.68	5.699%	$101.1328	$101.13	$101.15	$101.10
Purchase #2	$94.69	5.849%	$100.2284	$100.23	$100.25	$100.20
Purchase #3	$220.83	9.645%	$242.1291	$242.13	$242.15	$242.10
Purchase #4	$173.84	10.494%	$192.0828	$192.08	$192.10	$192.10
Purchase #5	$162.42	6.401%	$172.8165	$172.82	$172.80	$172.80
Purchase #6	$195.42	9.285%	$213.5647	$213.56	$213.55	$213.60
Purchase #7	$190.60	11.104%	$211.7642	$211.76	$211.75	$211.80
7 purchase totals =	$1,133.48		$1,233.7185	$1,233.71	$1,233.75	$1,233.70