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	$210.70	5.664%	$222.634	$222.63	$222.65	$222.60
Purchase #2	$185.88	8.702%	$202.0553	$202.06	$202.05	$202.10
Purchase #3	$48.73	12.410%	$54.7774	$54.78	$54.80	$54.80
Purchase #4	$45.62	5.558%	$48.1556	$48.16	$48.15	$48.20
Purchase #5	$80.52	12.675%	$90.7259	$90.73	$90.75	$90.70
Purchase #6	$69.49	12.563%	$78.22	$78.22	$78.20	$78.20
Purchase #7	$199.67	4.345%	$208.3457	$208.35	$208.35	$208.30
7 purchase totals =	$840.61		$904.9139	$904.93	$904.95	$904.90