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	$133.54	13.610%	$151.7148	$151.71	$151.70	$151.70
Purchase #2	$77.73	4.573%	$81.2846	$81.28	$81.30	$81.30
Purchase #3	$121.25	7.509%	$130.3547	$130.35	$130.35	$130.40
Purchase #4	$51.64	7.387%	$55.4546	$55.45	$55.45	$55.50
Purchase #5	$106.96	10.425%	$118.1106	$118.11	$118.10	$118.10
Purchase #6	$77.60	6.275%	$82.4694	$82.47	$82.45	$82.50
Purchase #7	$247.74	3.596%	$256.6487	$256.65	$256.65	$256.60
7 purchase totals =	$816.46		$876.0374	$876.02	$876.00	$876.10