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	$69.59	10.798%	$77.1043	$77.10	$77.10	$77.10
Purchase #2	$137.57	13.566%	$156.2327	$156.23	$156.25	$156.20
Purchase #3	$150.94	3.458%	$156.1595	$156.16	$156.15	$156.20
Purchase #4	$140.40	11.680%	$156.7987	$156.80	$156.80	$156.80
Purchase #5	$191.35	13.548%	$217.2741	$217.27	$217.25	$217.30
Purchase #6	$115.92	13.675%	$131.7721	$131.77	$131.75	$131.80
Purchase #7	$77.79	5.493%	$82.063	$82.06	$82.05	$82.10
7 purchase totals =	$883.56		$977.4044	$977.39	$977.35	$977.50