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	$233.55	9.787%	$256.4075	$256.41	$256.40	$256.40
Purchase #2	$153.74	13.457%	$174.4288	$174.43	$174.45	$174.40
Purchase #3	$58.39	7.583%	$62.8177	$62.82	$62.80	$62.80
Purchase #4	$185.26	10.427%	$204.5771	$204.58	$204.60	$204.60
Purchase #5	$15.41	6.626%	$16.4311	$16.43	$16.45	$16.40
Purchase #6	$63.40	5.339%	$66.7849	$66.78	$66.80	$66.80
Purchase #7	$136.59	4.646%	$142.936	$142.94	$142.95	$142.90
7 purchase totals =	$846.34		$924.3831	$924.39	$924.45	$924.30