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	$206.29	3.542%	$213.5968	$213.60	$213.60	$213.60
Purchase #2	$101.76	12.393%	$114.3711	$114.37	$114.35	$114.40
Purchase #3	$93.84	5.633%	$99.126	$99.13	$99.15	$99.10
Purchase #4	$16.71	10.732%	$18.5033	$18.50	$18.50	$18.50
Purchase #5	$57.42	5.172%	$60.3898	$60.39	$60.40	$60.40
Purchase #6	$102.42	11.640%	$114.3417	$114.34	$114.35	$114.30
Purchase #7	$233.57	12.552%	$262.8877	$262.89	$262.90	$262.90
7 purchase totals =	$812.01		$883.2164	$883.22	$883.25	$883.20