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	$244.35	13.543%	$277.4423	$277.44	$277.45	$277.40
Purchase #2	$212.81	13.525%	$241.5926	$241.59	$241.60	$241.60
Purchase #3	$81.37	5.377%	$85.7453	$85.75	$85.75	$85.70
Purchase #4	$52.28	13.800%	$59.4946	$59.49	$59.50	$59.50
Purchase #5	$109.35	6.582%	$116.5474	$116.55	$116.55	$116.50
Purchase #6	$125.61	7.189%	$134.6401	$134.64	$134.65	$134.60
Purchase #7	$76.60	12.787%	$86.3948	$86.39	$86.40	$86.40
7 purchase totals =	$902.37		$1,001.8571	$1,001.85	$1,001.90	$1,001.70