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	$166.29	5.592%	$175.5889	$175.59	$175.60	$175.60
Purchase #2	$124.34	6.579%	$132.5203	$132.52	$132.50	$132.50
Purchase #3	$54.41	13.827%	$61.9333	$61.93	$61.95	$61.90
Purchase #4	$211.35	3.843%	$219.4722	$219.47	$219.45	$219.50
Purchase #5	$184.38	8.829%	$200.6589	$200.66	$200.65	$200.70
Purchase #6	$150.98	4.283%	$157.4465	$157.45	$157.45	$157.40
Purchase #7	$127.61	8.859%	$138.915	$138.92	$138.90	$138.90
7 purchase totals =	$1,019.36		$1,086.5351	$1,086.54	$1,086.50	$1,086.50