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	$99.82	8.628%	$108.4325	$108.43	$108.45	$108.40
Purchase #2	$167.67	12.857%	$189.2273	$189.23	$189.25	$189.20
Purchase #3	$97.33	7.515%	$104.6443	$104.64	$104.65	$104.60
Purchase #4	$137.30	12.617%	$154.6231	$154.62	$154.60	$154.60
Purchase #5	$106.62	4.659%	$111.5874	$111.59	$111.60	$111.60
Purchase #6	$125.71	4.583%	$131.4713	$131.47	$131.45	$131.50
Purchase #7	$81.28	6.184%	$86.3064	$86.31	$86.30	$86.30
7 purchase totals =	$815.73		$886.2923	$886.29	$886.30	$886.20