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	$230.38	13.679%	$261.8937	$261.89	$261.90	$261.90
Purchase #2	$12.47	12.553%	$14.0354	$14.04	$14.05	$14.00
Purchase #3	$41.42	8.630%	$44.9945	$44.99	$45.00	$45.00
Purchase #4	$185.58	6.105%	$196.9097	$196.91	$196.90	$196.90
Purchase #5	$74.61	9.672%	$81.8263	$81.83	$81.85	$81.80
Purchase #6	$79.52	3.411%	$82.2324	$82.23	$82.25	$82.20
Purchase #7	$191.64	11.178%	$213.0615	$213.06	$213.05	$213.10
7 purchase totals =	$815.62		$894.9535	$894.95	$895.00	$894.90