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	$59.82	4.797%	$62.6896	$62.69	$62.70	$62.70
Purchase #2	$244.39	12.577%	$275.1269	$275.13	$275.15	$275.10
Purchase #3	$36.40	5.109%	$38.2597	$38.26	$38.25	$38.30
Purchase #4	$97.89	5.548%	$103.3209	$103.32	$103.30	$103.30
Purchase #5	$171.45	8.799%	$186.5359	$186.54	$186.55	$186.50
Purchase #6	$133.97	7.779%	$144.3915	$144.39	$144.40	$144.40
Purchase #7	$145.64	11.537%	$162.4425	$162.44	$162.45	$162.40
7 purchase totals =	$889.56		$972.7670	$972.77	$972.80	$972.70