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	$200.78	12.162%	$225.1989	$225.20	$225.20	$225.20
Purchase #2	$62.52	11.312%	$69.5923	$69.59	$69.60	$69.60
Purchase #3	$95.71	9.337%	$104.6464	$104.65	$104.65	$104.60
Purchase #4	$193.27	11.808%	$216.0913	$216.09	$216.10	$216.10
Purchase #5	$148.92	12.158%	$167.0257	$167.03	$167.05	$167.00
Purchase #6	$24.72	10.568%	$27.3324	$27.33	$27.35	$27.30
Purchase #7	$40.39	5.328%	$42.542	$42.54	$42.55	$42.50
7 purchase totals =	$766.31		$852.4290	$852.43	$852.50	$852.30