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	$154.73	8.801%	$168.3478	$168.35	$168.35	$168.30
Purchase #2	$77.87	11.835%	$87.0859	$87.09	$87.10	$87.10
Purchase #3	$111.89	10.337%	$123.4561	$123.46	$123.45	$123.50
Purchase #4	$129.69	5.822%	$137.2406	$137.24	$137.25	$137.20
Purchase #5	$200.58	6.289%	$213.1945	$213.19	$213.20	$213.20
Purchase #6	$25.29	12.544%	$28.4624	$28.46	$28.45	$28.50
Purchase #7	$60.58	10.437%	$66.9027	$66.90	$66.90	$66.90
7 purchase totals =	$760.63		$824.6900	$824.69	$824.70	$824.70