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	$89.91	7.366%	$96.5328	$96.53	$96.55	$96.50
Purchase #2	$80.61	4.745%	$84.4349	$84.43	$84.45	$84.40
Purchase #3	$71.76	9.464%	$78.5514	$78.55	$78.55	$78.60
Purchase #4	$21.93	3.180%	$22.6274	$22.63	$22.65	$22.60
Purchase #5	$103.71	12.440%	$116.6115	$116.61	$116.60	$116.60
Purchase #6	$105.60	10.680%	$116.8781	$116.88	$116.90	$116.90
Purchase #7	$90.29	8.648%	$98.0983	$98.10	$98.10	$98.10
7 purchase totals =	$563.81		$613.7344	$613.73	$613.80	$613.70