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	$117.89	11.575%	$131.5358	$131.54	$131.55	$131.50
Purchase #2	$164.34	9.652%	$180.2021	$180.20	$180.20	$180.20
Purchase #3	$181.49	9.203%	$198.1925	$198.19	$198.20	$198.20
Purchase #4	$154.69	11.488%	$172.4608	$172.46	$172.45	$172.50
Purchase #5	$49.53	13.455%	$56.1943	$56.19	$56.20	$56.20
Purchase #6	$144.67	9.440%	$158.3268	$158.33	$158.35	$158.30
Purchase #7	$223.92	4.675%	$234.3883	$234.39	$234.40	$234.40
7 purchase totals =	$1,036.53		$1,131.3006	$1,131.30	$1,131.35	$1,131.30