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	$83.27	4.324%	$86.8706	$86.87	$86.85	$86.90
Purchase #2	$48.60	3.105%	$50.109	$50.11	$50.10	$50.10
Purchase #3	$189.78	13.766%	$215.9051	$215.91	$215.90	$215.90
Purchase #4	$215.28	11.604%	$240.2611	$240.26	$240.25	$240.30
Purchase #5	$112.97	12.341%	$126.9116	$126.91	$126.90	$126.90
Purchase #6	$36.35	10.158%	$40.0424	$40.04	$40.05	$40.00
Purchase #7	$159.48	4.290%	$166.3217	$166.32	$166.30	$166.30
7 purchase totals =	$845.73		$926.4215	$926.42	$926.35	$926.40