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	$235.35	11.390%	$262.1564	$262.16	$262.15	$262.20
Purchase #2	$146.36	4.337%	$152.7076	$152.71	$152.70	$152.70
Purchase #3	$140.71	12.710%	$158.5942	$158.59	$158.60	$158.60
Purchase #4	$162.74	3.643%	$168.6686	$168.67	$168.65	$168.70
Purchase #5	$93.70	8.429%	$101.598	$101.60	$101.60	$101.60
Purchase #6	$243.31	13.870%	$277.0571	$277.06	$277.05	$277.10
Purchase #7	$186.91	5.242%	$196.7078	$196.71	$196.70	$196.70
7 purchase totals =	$1,209.08		$1,317.4897	$1,317.50	$1,317.45	$1,317.60