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	$60.80	12.793%	$68.5781	$68.58	$68.60	$68.60
Purchase #2	$131.55	9.685%	$144.2906	$144.29	$144.30	$144.30
Purchase #3	$187.28	4.344%	$195.4154	$195.42	$195.40	$195.40
Purchase #4	$73.72	6.434%	$78.4631	$78.46	$78.45	$78.50
Purchase #5	$209.89	12.723%	$236.5943	$236.59	$236.60	$236.60
Purchase #6	$194.51	12.426%	$218.6798	$218.68	$218.70	$218.70
Purchase #7	$89.31	13.512%	$101.3776	$101.38	$101.40	$101.40
7 purchase totals =	$947.06		$1,043.3989	$1,043.40	$1,043.45	$1,043.50