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	$58.48	10.372%	$64.5455	$64.55	$64.55	$64.50
Purchase #2	$136.69	4.399%	$142.703	$142.70	$142.70	$142.70
Purchase #3	$130.67	10.617%	$144.5432	$144.54	$144.55	$144.50
Purchase #4	$42.68	3.481%	$44.1657	$44.17	$44.15	$44.20
Purchase #5	$74.51	10.222%	$82.1264	$82.13	$82.15	$82.10
Purchase #6	$154.33	10.534%	$170.5871	$170.59	$170.60	$170.60
Purchase #7	$64.54	13.626%	$73.3342	$73.33	$73.35	$73.30
7 purchase totals =	$661.90		$722.0051	$722.01	$722.05	$721.90