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	$194.72	5.696%	$205.8113	$205.81	$205.80	$205.80
Purchase #2	$81.98	10.238%	$90.3731	$90.37	$90.35	$90.40
Purchase #3	$40.44	10.622%	$44.7355	$44.74	$44.75	$44.70
Purchase #4	$74.38	5.150%	$78.2106	$78.21	$78.20	$78.20
Purchase #5	$49.97	3.132%	$51.5351	$51.54	$51.55	$51.50
Purchase #6	$99.45	5.264%	$104.685	$104.69	$104.70	$104.70
Purchase #7	$181.78	4.125%	$189.2784	$189.28	$189.30	$189.30
7 purchase totals =	$722.72		$764.6290	$764.64	$764.65	$764.60