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	$66.97	10.687%	$74.1271	$74.13	$74.15	$74.10
Purchase #2	$17.47	6.211%	$18.5551	$18.56	$18.55	$18.60
Purchase #3	$58.73	7.628%	$63.2099	$63.21	$63.20	$63.20
Purchase #4	$131.64	12.648%	$148.2898	$148.29	$148.30	$148.30
Purchase #5	$138.89	3.210%	$143.3484	$143.35	$143.35	$143.30
Purchase #6	$92.31	13.832%	$105.0783	$105.08	$105.10	$105.10
Purchase #7	$68.68	6.132%	$72.8915	$72.89	$72.90	$72.90
7 purchase totals =	$574.69		$625.5001	$625.51	$625.55	$625.50