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	$189.50	11.155%	$210.6387	$210.64	$210.65	$210.60
Purchase #2	$36.52	13.217%	$41.3468	$41.35	$41.35	$41.30
Purchase #3	$134.53	12.493%	$151.3368	$151.34	$151.35	$151.30
Purchase #4	$145.39	3.264%	$150.1355	$150.14	$150.15	$150.10
Purchase #5	$227.43	11.278%	$253.0796	$253.08	$253.10	$253.10
Purchase #6	$222.64	8.537%	$241.6468	$241.65	$241.65	$241.60
Purchase #7	$164.68	13.866%	$187.5145	$187.51	$187.50	$187.50
7 purchase totals =	$1,120.69		$1,235.6987	$1,235.71	$1,235.75	$1,235.50