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	$62.60	4.673%	$65.5253	$65.53	$65.55	$65.50
Purchase #2	$119.80	3.173%	$123.6013	$123.60	$123.60	$123.60
Purchase #3	$108.72	13.443%	$123.3352	$123.34	$123.35	$123.30
Purchase #4	$137.99	5.604%	$145.723	$145.72	$145.70	$145.70
Purchase #5	$228.58	12.375%	$256.8668	$256.87	$256.85	$256.90
Purchase #6	$177.71	9.350%	$194.3259	$194.33	$194.35	$194.30
Purchase #7	$77.66	7.336%	$83.3571	$83.36	$83.35	$83.40
7 purchase totals =	$913.06		$992.7346	$992.75	$992.75	$992.70