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	$42.25	7.743%	$45.5214	$45.52	$45.50	$45.50
Purchase #2	$147.37	9.575%	$161.4807	$161.48	$161.50	$161.50
Purchase #3	$159.44	5.679%	$168.4946	$168.49	$168.50	$168.50
Purchase #4	$213.71	6.812%	$228.2679	$228.27	$228.25	$228.30
Purchase #5	$13.79	4.327%	$14.3867	$14.39	$14.40	$14.40
Purchase #6	$200.75	10.487%	$221.8027	$221.80	$221.80	$221.80
Purchase #7	$53.81	10.672%	$59.5526	$59.55	$59.55	$59.60
7 purchase totals =	$831.12		$899.5066	$899.50	$899.50	$899.60