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	$239.25	10.762%	$264.9981	$265.00	$265.00	$265.00
Purchase #2	$231.92	3.561%	$240.1787	$240.18	$240.20	$240.20
Purchase #3	$18.67	10.405%	$20.6126	$20.61	$20.60	$20.60
Purchase #4	$25.62	3.620%	$26.5474	$26.55	$26.55	$26.50
Purchase #5	$249.92	6.235%	$265.5025	$265.50	$265.50	$265.50
Purchase #6	$116.51	9.503%	$127.5819	$127.58	$127.60	$127.60
Purchase #7	$133.67	12.662%	$150.5953	$150.60	$150.60	$150.60
7 purchase totals =	$1,015.56		$1,096.0165	$1,096.02	$1,096.05	$1,096.00