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	$90.73	6.416%	$96.5512	$96.55	$96.55	$96.60
Purchase #2	$137.89	4.644%	$144.2936	$144.29	$144.30	$144.30
Purchase #3	$29.46	7.441%	$31.6521	$31.65	$31.65	$31.70
Purchase #4	$154.89	6.626%	$165.153	$165.15	$165.15	$165.20
Purchase #5	$248.89	5.297%	$262.0737	$262.07	$262.05	$262.10
Purchase #6	$116.79	13.384%	$132.4212	$132.42	$132.40	$132.40
Purchase #7	$139.88	5.322%	$147.3244	$147.32	$147.30	$147.30
7 purchase totals =	$918.53		$979.4692	$979.45	$979.40	$979.60