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	$91.39	6.222%	$97.0763	$97.08	$97.10	$97.10
Purchase #2	$118.60	7.609%	$127.6243	$127.62	$127.60	$127.60
Purchase #3	$92.94	6.629%	$99.101	$99.10	$99.10	$99.10
Purchase #4	$109.76	6.478%	$116.8703	$116.87	$116.85	$116.90
Purchase #5	$121.84	5.613%	$128.6789	$128.68	$128.70	$128.70
Purchase #6	$170.28	11.778%	$190.3356	$190.34	$190.35	$190.30
Purchase #7	$88.64	3.438%	$91.6874	$91.69	$91.70	$91.70
7 purchase totals =	$793.45		$851.3738	$851.38	$851.40	$851.40