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	$119.85	3.826%	$124.4355	$124.44	$124.45	$124.40
Purchase #2	$137.86	3.483%	$142.6617	$142.66	$142.65	$142.70
Purchase #3	$59.80	5.265%	$62.9485	$62.95	$62.95	$62.90
Purchase #4	$38.37	9.578%	$42.0451	$42.05	$42.05	$42.00
Purchase #5	$109.52	13.503%	$124.3085	$124.31	$124.30	$124.30
Purchase #6	$19.76	11.162%	$21.9656	$21.97	$21.95	$22.00
Purchase #7	$159.48	10.230%	$175.7948	$175.79	$175.80	$175.80
7 purchase totals =	$644.64		$694.1597	$694.17	$694.15	$694.10