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	$163.80	10.833%	$181.5445	$181.54	$181.55	$181.50
Purchase #2	$77.36	12.640%	$87.1383	$87.14	$87.15	$87.10
Purchase #3	$59.37	5.451%	$62.6063	$62.61	$62.60	$62.60
Purchase #4	$153.50	11.628%	$171.349	$171.35	$171.35	$171.30
Purchase #5	$7.46	5.664%	$7.8825	$7.88	$7.90	$7.90
Purchase #6	$15.53	13.504%	$17.6272	$17.63	$17.65	$17.60
Purchase #7	$54.54	12.167%	$61.1759	$61.18	$61.20	$61.20
7 purchase totals =	$531.56		$589.3237	$589.33	$589.40	$589.20