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	$249.54	5.141%	$262.3689	$262.37	$262.35	$262.40
Purchase #2	$174.95	7.337%	$187.7861	$187.79	$187.80	$187.80
Purchase #3	$29.38	4.836%	$30.8008	$30.80	$30.80	$30.80
Purchase #4	$57.46	13.853%	$65.4199	$65.42	$65.40	$65.40
Purchase #5	$155.32	12.298%	$174.4213	$174.42	$174.40	$174.40
Purchase #6	$58.61	6.565%	$62.4577	$62.46	$62.45	$62.50
Purchase #7	$131.56	5.603%	$138.9313	$138.93	$138.95	$138.90
7 purchase totals =	$856.82		$922.1860	$922.19	$922.15	$922.20