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	$163.65	5.580%	$172.7817	$172.78	$172.80	$172.80
Purchase #2	$231.78	9.408%	$253.5859	$253.59	$253.60	$253.60
Purchase #3	$13.59	3.846%	$14.1127	$14.11	$14.10	$14.10
Purchase #4	$104.86	11.823%	$117.2576	$117.26	$117.25	$117.30
Purchase #5	$182.43	12.154%	$204.6025	$204.60	$204.60	$204.60
Purchase #6	$40.70	3.480%	$42.1164	$42.12	$42.10	$42.10
Purchase #7	$10.70	6.739%	$11.4211	$11.42	$11.40	$11.40
7 purchase totals =	$747.71		$815.8779	$815.88	$815.85	$815.90