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	$88.27	9.446%	$96.608	$96.61	$96.60	$96.60
Purchase #2	$212.27	4.162%	$221.1047	$221.10	$221.10	$221.10
Purchase #3	$138.70	12.248%	$155.688	$155.69	$155.70	$155.70
Purchase #4	$226.38	8.828%	$246.3648	$246.36	$246.35	$246.40
Purchase #5	$166.85	11.114%	$185.3937	$185.39	$185.40	$185.40
Purchase #6	$75.95	8.146%	$82.1369	$82.14	$82.15	$82.10
Purchase #7	$196.60	13.184%	$222.5197	$222.52	$222.50	$222.50
7 purchase totals =	$1,105.02		$1,209.8158	$1,209.81	$1,209.80	$1,209.80