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	$126.90	4.301%	$132.358	$132.36	$132.35	$132.40
Purchase #2	$90.38	4.512%	$94.4579	$94.46	$94.45	$94.50
Purchase #3	$51.35	7.393%	$55.1463	$55.15	$55.15	$55.10
Purchase #4	$83.74	4.396%	$87.4212	$87.42	$87.40	$87.40
Purchase #5	$186.47	5.224%	$196.2112	$196.21	$196.20	$196.20
Purchase #6	$51.94	10.715%	$57.5054	$57.51	$57.50	$57.50
Purchase #7	$23.46	4.227%	$24.4517	$24.45	$24.45	$24.50
7 purchase totals =	$614.24		$647.5517	$647.56	$647.50	$647.60