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	$214.53	7.849%	$231.3685	$231.37	$231.35	$231.40
Purchase #2	$242.77	12.661%	$273.5071	$273.51	$273.50	$273.50
Purchase #3	$35.66	7.595%	$38.3684	$38.37	$38.35	$38.40
Purchase #4	$137.45	5.176%	$144.5644	$144.56	$144.55	$144.60
Purchase #5	$14.77	7.510%	$15.8792	$15.88	$15.90	$15.90
Purchase #6	$178.39	11.597%	$199.0779	$199.08	$199.10	$199.10
Purchase #7	$136.37	9.356%	$149.1288	$149.13	$149.15	$149.10
7 purchase totals =	$959.94		$1,051.8943	$1,051.90	$1,051.90	$1,052.00