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	$91.47	10.366%	$100.9518	$100.95	$100.95	$101.00
Purchase #2	$134.27	10.303%	$148.1038	$148.10	$148.10	$148.10
Purchase #3	$218.27	3.208%	$225.2721	$225.27	$225.25	$225.30
Purchase #4	$132.88	4.493%	$138.8503	$138.85	$138.85	$138.90
Purchase #5	$125.86	3.470%	$130.2273	$130.23	$130.25	$130.20
Purchase #6	$169.94	12.610%	$191.3694	$191.37	$191.35	$191.40
Purchase #7	$185.45	3.259%	$191.4938	$191.49	$191.50	$191.50
7 purchase totals =	$1,058.14		$1,126.2685	$1,126.26	$1,126.25	$1,126.40