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	$167.46	7.451%	$179.9374	$179.94	$179.95	$179.90
Purchase #2	$29.80	5.800%	$31.5284	$31.53	$31.55	$31.50
Purchase #3	$132.72	8.447%	$143.9309	$143.93	$143.95	$143.90
Purchase #4	$34.94	7.111%	$37.4246	$37.42	$37.40	$37.40
Purchase #5	$141.41	4.229%	$147.3902	$147.39	$147.40	$147.40
Purchase #6	$75.98	9.695%	$83.3463	$83.35	$83.35	$83.30
Purchase #7	$78.60	11.151%	$87.3647	$87.36	$87.35	$87.40
7 purchase totals =	$660.91		$710.9225	$710.92	$710.95	$710.80