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	$82.81	7.760%	$89.2361	$89.24	$89.25	$89.20
Purchase #2	$133.61	8.217%	$144.5887	$144.59	$144.60	$144.60
Purchase #3	$184.38	13.783%	$209.7931	$209.79	$209.80	$209.80
Purchase #4	$175.88	6.460%	$187.2418	$187.24	$187.25	$187.20
Purchase #5	$108.50	3.746%	$112.5644	$112.56	$112.55	$112.60
Purchase #6	$149.45	5.249%	$157.2946	$157.29	$157.30	$157.30
Purchase #7	$150.52	9.406%	$164.6779	$164.68	$164.70	$164.70
7 purchase totals =	$985.15		$1,065.3966	$1,065.39	$1,065.45	$1,065.40