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	$76.47	8.141%	$82.6954	$82.70	$82.70	$82.70
Purchase #2	$65.70	8.409%	$71.2247	$71.22	$71.20	$71.20
Purchase #3	$82.54	12.340%	$92.7254	$92.73	$92.75	$92.70
Purchase #4	$164.76	3.535%	$170.5843	$170.58	$170.60	$170.60
Purchase #5	$206.42	5.357%	$217.4779	$217.48	$217.50	$217.50
Purchase #6	$125.58	10.333%	$138.5562	$138.56	$138.55	$138.60
Purchase #7	$187.46	9.474%	$205.22	$205.22	$205.20	$205.20
7 purchase totals =	$908.93		$978.4839	$978.49	$978.50	$978.50