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	$86.68	9.214%	$94.6667	$94.67	$94.65	$94.70
Purchase #2	$130.62	5.397%	$137.6696	$137.67	$137.65	$137.70
Purchase #3	$147.46	12.226%	$165.4885	$165.49	$165.50	$165.50
Purchase #4	$84.71	5.699%	$89.5376	$89.54	$89.55	$89.50
Purchase #5	$99.79	13.755%	$113.5161	$113.52	$113.50	$113.50
Purchase #6	$220.92	3.300%	$228.2104	$228.21	$228.20	$228.20
Purchase #7	$227.25	13.716%	$258.4196	$258.42	$258.40	$258.40
7 purchase totals =	$997.43		$1,087.5085	$1,087.52	$1,087.45	$1,087.50