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	$51.61	13.564%	$58.6104	$58.61	$58.60	$58.60
Purchase #2	$78.37	6.225%	$83.2485	$83.25	$83.25	$83.20
Purchase #3	$19.92	13.677%	$22.6445	$22.64	$22.65	$22.60
Purchase #4	$158.79	3.505%	$164.3556	$164.36	$164.35	$164.40
Purchase #5	$71.32	12.233%	$80.0446	$80.04	$80.05	$80.00
Purchase #6	$98.59	13.434%	$111.8346	$111.83	$111.85	$111.80
Purchase #7	$50.89	3.311%	$52.575	$52.58	$52.60	$52.60
7 purchase totals =	$529.49		$573.3132	$573.31	$573.35	$573.20