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	$154.48	5.410%	$162.8374	$162.84	$162.85	$162.80
Purchase #2	$145.45	13.332%	$164.8414	$164.84	$164.85	$164.80
Purchase #3	$31.59	6.401%	$33.6121	$33.61	$33.60	$33.60
Purchase #4	$238.96	7.453%	$256.7697	$256.77	$256.75	$256.80
Purchase #5	$68.71	13.859%	$78.2325	$78.23	$78.25	$78.20
Purchase #6	$116.67	10.505%	$128.9262	$128.93	$128.95	$128.90
Purchase #7	$20.77	5.288%	$21.8683	$21.87	$21.85	$21.90
7 purchase totals =	$776.63		$847.0876	$847.09	$847.10	$847.00