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	$230.42	4.464%	$240.7059	$240.71	$240.70	$240.70
Purchase #2	$131.90	8.694%	$143.3674	$143.37	$143.35	$143.40
Purchase #3	$92.42	7.534%	$99.3829	$99.38	$99.40	$99.40
Purchase #4	$203.60	12.564%	$229.1803	$229.18	$229.20	$229.20
Purchase #5	$153.25	12.423%	$172.2882	$172.29	$172.30	$172.30
Purchase #6	$129.28	3.834%	$134.2366	$134.24	$134.25	$134.20
Purchase #7	$119.67	3.334%	$123.6598	$123.66	$123.65	$123.70
7 purchase totals =	$1,060.54		$1,142.8211	$1,142.83	$1,142.85	$1,142.90