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	$88.86	3.720%	$92.1656	$92.17	$92.15	$92.20
Purchase #2	$48.60	7.726%	$52.3548	$52.35	$52.35	$52.40
Purchase #3	$90.69	10.191%	$99.9322	$99.93	$99.95	$99.90
Purchase #4	$104.41	8.178%	$112.9486	$112.95	$112.95	$112.90
Purchase #5	$137.32	13.815%	$156.2908	$156.29	$156.30	$156.30
Purchase #6	$101.98	6.859%	$108.9748	$108.97	$108.95	$109.00
Purchase #7	$137.78	6.108%	$146.1956	$146.20	$146.20	$146.20
7 purchase totals =	$709.64		$768.8624	$768.86	$768.85	$768.90