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	$49.96	7.307%	$53.6106	$53.61	$53.60	$53.60
Purchase #2	$14.94	3.785%	$15.5055	$15.51	$15.50	$15.50
Purchase #3	$192.94	11.635%	$215.3886	$215.39	$215.40	$215.40
Purchase #4	$188.47	12.773%	$212.5433	$212.54	$212.55	$212.50
Purchase #5	$136.71	7.217%	$146.5764	$146.58	$146.60	$146.60
Purchase #6	$184.72	8.240%	$199.9409	$199.94	$199.95	$199.90
Purchase #7	$188.95	13.765%	$214.959	$214.96	$214.95	$215.00
7 purchase totals =	$956.69		$1,058.5243	$1,058.53	$1,058.55	$1,058.50