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	$105.32	6.111%	$111.7561	$111.76	$111.75	$111.80
Purchase #2	$195.42	9.435%	$213.8579	$213.86	$213.85	$213.90
Purchase #3	$183.97	4.611%	$192.4529	$192.45	$192.45	$192.50
Purchase #4	$121.83	4.782%	$127.6559	$127.66	$127.65	$127.70
Purchase #5	$93.42	8.560%	$101.4168	$101.42	$101.40	$101.40
Purchase #6	$154.32	6.753%	$164.7412	$164.74	$164.75	$164.70
Purchase #7	$5.95	11.806%	$6.6525	$6.65	$6.65	$6.70
7 purchase totals =	$860.23		$918.5333	$918.54	$918.50	$918.70