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	$130.60	13.564%	$148.3146	$148.31	$148.30	$148.30
Purchase #2	$148.29	10.847%	$164.375	$164.38	$164.40	$164.40
Purchase #3	$114.65	10.286%	$126.4429	$126.44	$126.45	$126.40
Purchase #4	$73.71	6.122%	$78.2225	$78.22	$78.20	$78.20
Purchase #5	$213.61	6.671%	$227.8599	$227.86	$227.85	$227.90
Purchase #6	$200.57	7.801%	$216.2165	$216.22	$216.20	$216.20
Purchase #7	$111.33	5.871%	$117.8662	$117.87	$117.85	$117.90
7 purchase totals =	$992.76		$1,079.2976	$1,079.30	$1,079.25	$1,079.30