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	$118.97	9.558%	$130.3412	$130.34	$130.35	$130.30
Purchase #2	$102.93	8.135%	$111.3034	$111.30	$111.30	$111.30
Purchase #3	$132.85	9.771%	$145.8308	$145.83	$145.85	$145.80
Purchase #4	$73.85	10.219%	$81.3967	$81.40	$81.40	$81.40
Purchase #5	$179.86	6.545%	$191.6318	$191.63	$191.65	$191.60
Purchase #6	$125.96	13.210%	$142.5993	$142.60	$142.60	$142.60
Purchase #7	$193.97	10.865%	$215.0448	$215.04	$215.05	$215.00
7 purchase totals =	$928.39		$1,018.1480	$1,018.14	$1,018.20	$1,018.00