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	$165.64	11.547%	$184.7665	$184.77	$184.75	$184.80
Purchase #2	$126.59	12.419%	$142.3112	$142.31	$142.30	$142.30
Purchase #3	$86.95	4.196%	$90.5984	$90.60	$90.60	$90.60
Purchase #4	$200.38	7.244%	$214.8955	$214.90	$214.90	$214.90
Purchase #5	$190.79	8.798%	$207.5757	$207.58	$207.60	$207.60
Purchase #6	$52.30	9.233%	$57.1289	$57.13	$57.15	$57.10
Purchase #7	$185.33	6.414%	$197.2171	$197.22	$197.20	$197.20
7 purchase totals =	$1,007.98		$1,094.4933	$1,094.51	$1,094.50	$1,094.50