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	$137.62	11.272%	$153.1325	$153.13	$153.15	$153.10
Purchase #2	$11.98	10.752%	$13.2681	$13.27	$13.25	$13.30
Purchase #3	$172.52	3.776%	$179.0344	$179.03	$179.05	$179.00
Purchase #4	$64.32	10.635%	$71.1604	$71.16	$71.15	$71.20
Purchase #5	$126.46	3.566%	$130.9696	$130.97	$130.95	$131.00
Purchase #6	$161.25	9.534%	$176.6236	$176.62	$176.60	$176.60
Purchase #7	$70.30	3.620%	$72.8449	$72.84	$72.85	$72.80
7 purchase totals =	$744.45		$797.0335	$797.02	$797.00	$797.00