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	$126.84	12.225%	$142.3462	$142.35	$142.35	$142.30
Purchase #2	$43.96	9.685%	$48.2175	$48.22	$48.20	$48.20
Purchase #3	$73.77	11.209%	$82.0389	$82.04	$82.05	$82.00
Purchase #4	$43.46	5.680%	$45.9285	$45.93	$45.95	$45.90
Purchase #5	$238.28	11.829%	$266.4661	$266.47	$266.45	$266.50
Purchase #6	$63.37	5.597%	$66.9168	$66.92	$66.90	$66.90
Purchase #7	$48.91	12.774%	$55.1578	$55.16	$55.15	$55.20
7 purchase totals =	$638.59		$707.0718	$707.09	$707.05	$707.00