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	$133.77	8.707%	$145.4174	$145.42	$145.40	$145.40
Purchase #2	$232.27	10.386%	$256.3936	$256.39	$256.40	$256.40
Purchase #3	$77.53	8.542%	$84.1526	$84.15	$84.15	$84.20
Purchase #4	$139.58	11.621%	$155.8006	$155.80	$155.80	$155.80
Purchase #5	$56.40	5.569%	$59.5409	$59.54	$59.55	$59.50
Purchase #6	$217.49	4.284%	$226.8073	$226.81	$226.80	$226.80
Purchase #7	$86.92	3.144%	$89.6528	$89.65	$89.65	$89.70
7 purchase totals =	$943.96		$1,017.7652	$1,017.76	$1,017.75	$1,017.80