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	$223.42	5.605%	$235.9427	$235.94	$235.95	$235.90
Purchase #2	$85.54	5.350%	$90.1164	$90.12	$90.10	$90.10
Purchase #3	$208.64	5.722%	$220.5784	$220.58	$220.60	$220.60
Purchase #4	$196.37	13.709%	$223.2904	$223.29	$223.30	$223.30
Purchase #5	$131.29	4.817%	$137.6142	$137.61	$137.60	$137.60
Purchase #6	$81.77	10.184%	$90.0975	$90.10	$90.10	$90.10
Purchase #7	$147.53	9.774%	$161.9496	$161.95	$161.95	$161.90
7 purchase totals =	$1,074.56		$1,159.5892	$1,159.59	$1,159.60	$1,159.50