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	$176.37	11.641%	$196.9012	$196.90	$196.90	$196.90
Purchase #2	$132.35	11.864%	$148.052	$148.05	$148.05	$148.10
Purchase #3	$238.47	13.607%	$270.9186	$270.92	$270.90	$270.90
Purchase #4	$191.48	3.356%	$197.9061	$197.91	$197.90	$197.90
Purchase #5	$87.99	5.132%	$92.5056	$92.51	$92.50	$92.50
Purchase #6	$186.58	3.308%	$192.7521	$192.75	$192.75	$192.80
Purchase #7	$227.26	12.814%	$256.3811	$256.38	$256.40	$256.40
7 purchase totals =	$1,240.50		$1,355.4167	$1,355.42	$1,355.40	$1,355.50