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	$78.34	9.550%	$85.8215	$85.82	$85.80	$85.80
Purchase #2	$155.41	6.526%	$165.5521	$165.55	$165.55	$165.60
Purchase #3	$55.25	6.548%	$58.8678	$58.87	$58.85	$58.90
Purchase #4	$25.58	8.191%	$27.6753	$27.68	$27.70	$27.70
Purchase #5	$156.70	5.125%	$164.7309	$164.73	$164.75	$164.70
Purchase #6	$237.80	11.477%	$265.0923	$265.09	$265.10	$265.10
Purchase #7	$91.67	9.383%	$100.2714	$100.27	$100.25	$100.30
7 purchase totals =	$800.75		$868.0113	$868.01	$868.00	$868.10