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	$12.71	12.283%	$14.2712	$14.27	$14.25	$14.30
Purchase #2	$208.77	8.205%	$225.8996	$225.90	$225.90	$225.90
Purchase #3	$104.46	10.472%	$115.3991	$115.40	$115.40	$115.40
Purchase #4	$150.98	11.700%	$168.6447	$168.64	$168.65	$168.60
Purchase #5	$47.93	5.671%	$50.6481	$50.65	$50.65	$50.60
Purchase #6	$206.82	4.283%	$215.6781	$215.68	$215.70	$215.70
Purchase #7	$238.56	8.522%	$258.8901	$258.89	$258.90	$258.90
7 purchase totals =	$970.23		$1,049.4309	$1,049.43	$1,049.45	$1,049.40