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	$47.49	13.800%	$54.0436	$54.04	$54.05	$54.00
Purchase #2	$116.37	7.145%	$124.6846	$124.68	$124.70	$124.70
Purchase #3	$243.38	4.706%	$254.8335	$254.83	$254.85	$254.80
Purchase #4	$55.51	5.423%	$58.5203	$58.52	$58.50	$58.50
Purchase #5	$54.39	13.649%	$61.8137	$61.81	$61.80	$61.80
Purchase #6	$115.97	6.242%	$123.2088	$123.21	$123.20	$123.20
Purchase #7	$137.50	5.386%	$144.9058	$144.91	$144.90	$144.90
7 purchase totals =	$770.61		$822.0103	$822.00	$822.00	$821.90