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	$142.73	9.193%	$155.8512	$155.85	$155.85	$155.90
Purchase #2	$75.67	9.579%	$82.9184	$82.92	$82.90	$82.90
Purchase #3	$187.86	11.583%	$209.6198	$209.62	$209.60	$209.60
Purchase #4	$56.41	10.606%	$62.3928	$62.39	$62.40	$62.40
Purchase #5	$134.26	5.327%	$141.412	$141.41	$141.40	$141.40
Purchase #6	$223.49	12.463%	$251.3436	$251.34	$251.35	$251.30
Purchase #7	$99.91	4.617%	$104.5228	$104.52	$104.50	$104.50
7 purchase totals =	$920.33		$1,008.0606	$1,008.05	$1,008.00	$1,008.00