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	$182.77	4.669%	$191.3035	$191.30	$191.30	$191.30
Purchase #2	$41.42	4.775%	$43.3978	$43.40	$43.40	$43.40
Purchase #3	$166.92	12.447%	$187.6965	$187.70	$187.70	$187.70
Purchase #4	$237.45	3.377%	$245.4687	$245.47	$245.45	$245.50
Purchase #5	$53.35	5.665%	$56.3723	$56.37	$56.35	$56.40
Purchase #6	$187.97	6.540%	$200.2632	$200.26	$200.25	$200.30
Purchase #7	$235.34	8.652%	$255.7016	$255.70	$255.70	$255.70
7 purchase totals =	$1,105.22		$1,180.2036	$1,180.20	$1,180.15	$1,180.30