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	$90.57	10.437%	$100.0228	$100.02	$100.00	$100.00
Purchase #2	$65.53	10.259%	$72.2527	$72.25	$72.25	$72.30
Purchase #3	$120.93	4.584%	$126.4734	$126.47	$126.45	$126.50
Purchase #4	$91.35	4.574%	$95.5283	$95.53	$95.55	$95.50
Purchase #5	$239.60	12.366%	$269.2289	$269.23	$269.25	$269.20
Purchase #6	$168.64	12.617%	$189.9173	$189.92	$189.90	$189.90
Purchase #7	$120.31	9.757%	$132.0486	$132.05	$132.05	$132.00
7 purchase totals =	$896.93		$985.4720	$985.47	$985.45	$985.40