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	$9.44	12.151%	$10.5871	$10.59	$10.60	$10.60
Purchase #2	$88.88	3.261%	$91.7784	$91.78	$91.80	$91.80
Purchase #3	$15.64	10.608%	$17.2991	$17.30	$17.30	$17.30
Purchase #4	$60.49	11.597%	$67.505	$67.51	$67.50	$67.50
Purchase #5	$120.55	9.748%	$132.3012	$132.30	$132.30	$132.30
Purchase #6	$53.30	3.309%	$55.0637	$55.06	$55.05	$55.10
Purchase #7	$142.25	6.859%	$152.0069	$152.01	$152.00	$152.00
7 purchase totals =	$490.55		$526.5414	$526.55	$526.55	$526.60