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	$100.78	4.553%	$105.3685	$105.37	$105.35	$105.40
Purchase #2	$150.97	7.694%	$162.5856	$162.59	$162.60	$162.60
Purchase #3	$231.48	10.451%	$255.672	$255.67	$255.65	$255.70
Purchase #4	$80.40	13.217%	$91.0265	$91.03	$91.05	$91.00
Purchase #5	$127.68	13.417%	$144.8108	$144.81	$144.80	$144.80
Purchase #6	$27.86	5.666%	$29.4385	$29.44	$29.45	$29.40
Purchase #7	$240.81	6.849%	$257.3031	$257.30	$257.30	$257.30
7 purchase totals =	$959.98		$1,046.2050	$1,046.21	$1,046.20	$1,046.20