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	$155.43	11.804%	$173.777	$173.78	$173.80	$173.80
Purchase #2	$234.61	10.355%	$258.9039	$258.90	$258.90	$258.90
Purchase #3	$56.46	10.226%	$62.2336	$62.23	$62.25	$62.20
Purchase #4	$54.81	9.144%	$59.8218	$59.82	$59.80	$59.80
Purchase #5	$210.51	3.397%	$217.661	$217.66	$217.65	$217.70
Purchase #6	$208.51	8.245%	$225.7016	$225.70	$225.70	$225.70
Purchase #7	$114.98	13.677%	$130.7058	$130.71	$130.70	$130.70
7 purchase totals =	$1,035.31		$1,128.8047	$1,128.80	$1,128.80	$1,128.80