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	$127.69	7.498%	$137.2642	$137.26	$137.25	$137.30
Purchase #2	$40.78	4.565%	$42.6416	$42.64	$42.65	$42.60
Purchase #3	$127.93	4.842%	$134.1244	$134.12	$134.10	$134.10
Purchase #4	$48.92	10.553%	$54.0825	$54.08	$54.10	$54.10
Purchase #5	$154.42	8.483%	$167.5194	$167.52	$167.50	$167.50
Purchase #6	$13.81	8.819%	$15.0279	$15.03	$15.05	$15.00
Purchase #7	$75.52	8.628%	$82.0359	$82.04	$82.05	$82.00
7 purchase totals =	$589.07		$632.6959	$632.69	$632.70	$632.60