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	$208.94	5.103%	$219.6022	$219.60	$219.60	$219.60
Purchase #2	$187.68	13.741%	$213.4691	$213.47	$213.45	$213.50
Purchase #3	$206.59	3.137%	$213.0707	$213.07	$213.05	$213.10
Purchase #4	$104.54	6.549%	$111.3863	$111.39	$111.40	$111.40
Purchase #5	$131.42	12.109%	$147.3336	$147.33	$147.35	$147.30
Purchase #6	$20.46	7.799%	$22.0557	$22.06	$22.05	$22.10
Purchase #7	$130.47	8.412%	$141.4451	$141.45	$141.45	$141.40
7 purchase totals =	$990.10		$1,068.3627	$1,068.37	$1,068.35	$1,068.40