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	$56.42	9.827%	$61.9644	$61.96	$61.95	$62.00
Purchase #2	$78.91	5.851%	$83.527	$83.53	$83.55	$83.50
Purchase #3	$96.43	12.587%	$108.5676	$108.57	$108.55	$108.60
Purchase #4	$146.69	6.632%	$156.4185	$156.42	$156.40	$156.40
Purchase #5	$79.72	13.480%	$90.4663	$90.47	$90.45	$90.50
Purchase #6	$99.87	7.354%	$107.2144	$107.21	$107.20	$107.20
Purchase #7	$14.85	3.677%	$15.396	$15.40	$15.40	$15.40
7 purchase totals =	$572.89		$623.5542	$623.56	$623.50	$623.60