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	$63.82	3.204%	$65.8648	$65.86	$65.85	$65.90
Purchase #2	$107.95	8.270%	$116.8775	$116.88	$116.90	$116.90
Purchase #3	$196.75	4.848%	$206.2884	$206.29	$206.30	$206.30
Purchase #4	$79.30	7.534%	$85.2745	$85.27	$85.25	$85.30
Purchase #5	$37.36	9.356%	$40.8554	$40.86	$40.85	$40.90
Purchase #6	$105.37	3.365%	$108.9157	$108.92	$108.90	$108.90
Purchase #7	$90.78	8.613%	$98.5989	$98.60	$98.60	$98.60
7 purchase totals =	$681.33		$722.6752	$722.68	$722.65	$722.80