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	$212.45	10.429%	$234.6064	$234.61	$234.60	$234.60
Purchase #2	$56.80	5.453%	$59.8973	$59.90	$59.90	$59.90
Purchase #3	$201.38	5.388%	$212.2304	$212.23	$212.25	$212.20
Purchase #4	$59.87	10.715%	$66.2851	$66.29	$66.30	$66.30
Purchase #5	$44.94	10.844%	$49.8133	$49.81	$49.80	$49.80
Purchase #6	$45.64	4.769%	$47.8166	$47.82	$47.80	$47.80
Purchase #7	$77.77	5.308%	$81.898	$81.90	$81.90	$81.90
7 purchase totals =	$698.85		$752.5471	$752.56	$752.55	$752.50