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	$229.48	3.715%	$238.0052	$238.01	$238.00	$238.00
Purchase #2	$154.71	5.632%	$163.4233	$163.42	$163.40	$163.40
Purchase #3	$150.31	9.286%	$164.2678	$164.27	$164.25	$164.30
Purchase #4	$75.82	3.255%	$78.2879	$78.29	$78.30	$78.30
Purchase #5	$190.70	4.371%	$199.0355	$199.04	$199.05	$199.00
Purchase #6	$194.38	3.193%	$200.5866	$200.59	$200.60	$200.60
Purchase #7	$164.64	6.191%	$174.8329	$174.83	$174.85	$174.80
7 purchase totals =	$1,160.04		$1,218.4392	$1,218.45	$1,218.45	$1,218.40