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	$228.56	13.129%	$258.5676	$258.57	$258.55	$258.60
Purchase #2	$96.28	4.442%	$100.5568	$100.56	$100.55	$100.60
Purchase #3	$215.28	3.725%	$223.2992	$223.30	$223.30	$223.30
Purchase #4	$144.62	13.845%	$164.6426	$164.64	$164.65	$164.60
Purchase #5	$95.59	13.647%	$108.6352	$108.64	$108.65	$108.60
Purchase #6	$169.48	4.322%	$176.8049	$176.80	$176.80	$176.80
Purchase #7	$216.38	6.230%	$229.8605	$229.86	$229.85	$229.90
7 purchase totals =	$1,166.19		$1,262.3668	$1,262.37	$1,262.35	$1,262.40