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	$70.40	11.787%	$78.698	$78.70	$78.70	$78.70
Purchase #2	$192.48	12.593%	$216.719	$216.72	$216.70	$216.70
Purchase #3	$132.84	5.599%	$140.2777	$140.28	$140.30	$140.30
Purchase #4	$66.39	9.599%	$72.7628	$72.76	$72.75	$72.80
Purchase #5	$139.47	3.323%	$144.1046	$144.10	$144.10	$144.10
Purchase #6	$176.26	10.579%	$194.9065	$194.91	$194.90	$194.90
Purchase #7	$121.27	4.292%	$126.4749	$126.47	$126.45	$126.50
7 purchase totals =	$899.11		$973.9435	$973.94	$973.90	$974.00