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	$85.52	4.162%	$89.0793	$89.08	$89.10	$89.10
Purchase #2	$19.52	5.162%	$20.5276	$20.53	$20.55	$20.50
Purchase #3	$128.81	4.265%	$134.3037	$134.30	$134.30	$134.30
Purchase #4	$191.44	13.596%	$217.4682	$217.47	$217.45	$217.50
Purchase #5	$111.88	11.803%	$125.0852	$125.09	$125.10	$125.10
Purchase #6	$222.50	4.807%	$233.1956	$233.20	$233.20	$233.20
Purchase #7	$179.47	10.522%	$198.3538	$198.35	$198.35	$198.40
7 purchase totals =	$939.14		$1,018.0134	$1,018.02	$1,018.05	$1,018.10