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	$66.37	9.439%	$72.6347	$72.63	$72.65	$72.60
Purchase #2	$210.51	10.184%	$231.9483	$231.95	$231.95	$231.90
Purchase #3	$141.39	9.518%	$154.8475	$154.85	$154.85	$154.80
Purchase #4	$234.78	11.821%	$262.5333	$262.53	$262.55	$262.50
Purchase #5	$241.63	10.624%	$267.3008	$267.30	$267.30	$267.30
Purchase #6	$127.29	9.113%	$138.8899	$138.89	$138.90	$138.90
Purchase #7	$134.76	9.393%	$147.418	$147.42	$147.40	$147.40
7 purchase totals =	$1,156.73		$1,275.5725	$1,275.57	$1,275.60	$1,275.40