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	$23.82	8.545%	$25.8554	$25.86	$25.85	$25.90
Purchase #2	$61.30	6.623%	$65.3599	$65.36	$65.35	$65.40
Purchase #3	$170.83	11.383%	$190.2756	$190.28	$190.30	$190.30
Purchase #4	$215.78	4.848%	$226.241	$226.24	$226.25	$226.20
Purchase #5	$151.51	10.595%	$167.5625	$167.56	$167.55	$167.60
Purchase #6	$40.31	13.615%	$45.7982	$45.80	$45.80	$45.80
Purchase #7	$230.34	8.227%	$249.2901	$249.29	$249.30	$249.30
7 purchase totals =	$893.89		$970.3827	$970.39	$970.40	$970.50