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	$48.68	11.745%	$54.3975	$54.40	$54.40	$54.40
Purchase #2	$140.78	12.542%	$158.4366	$158.44	$158.45	$158.40
Purchase #3	$186.86	13.624%	$212.3178	$212.32	$212.30	$212.30
Purchase #4	$154.44	6.457%	$164.4122	$164.41	$164.40	$164.40
Purchase #5	$11.74	12.254%	$13.1786	$13.18	$13.20	$13.20
Purchase #6	$17.35	4.158%	$18.0714	$18.07	$18.05	$18.10
Purchase #7	$152.72	5.154%	$160.5912	$160.59	$160.60	$160.60
7 purchase totals =	$712.57		$781.4053	$781.41	$781.40	$781.40