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	$111.88	13.112%	$126.5497	$126.55	$126.55	$126.50
Purchase #2	$176.76	12.537%	$198.9204	$198.92	$198.90	$198.90
Purchase #3	$36.67	12.297%	$41.1793	$41.18	$41.20	$41.20
Purchase #4	$126.72	10.586%	$140.1346	$140.13	$140.15	$140.10
Purchase #5	$40.38	6.512%	$43.0095	$43.01	$43.00	$43.00
Purchase #6	$13.95	4.393%	$14.5628	$14.56	$14.55	$14.60
Purchase #7	$133.95	13.345%	$151.8256	$151.83	$151.85	$151.80
7 purchase totals =	$640.31		$716.1819	$716.18	$716.20	$716.10