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	$94.74	11.326%	$105.4703	$105.47	$105.45	$105.50
Purchase #2	$14.35	3.293%	$14.8225	$14.82	$14.80	$14.80
Purchase #3	$129.45	8.748%	$140.7743	$140.77	$140.75	$140.80
Purchase #4	$169.37	12.578%	$190.6734	$190.67	$190.65	$190.70
Purchase #5	$29.67	12.286%	$33.3153	$33.32	$33.30	$33.30
Purchase #6	$201.89	9.545%	$221.1604	$221.16	$221.15	$221.20
Purchase #7	$243.91	11.755%	$272.5816	$272.58	$272.60	$272.60
7 purchase totals =	$883.38		$978.7978	$978.79	$978.70	$978.90