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	$125.46	5.822%	$132.7643	$132.76	$132.75	$132.80
Purchase #2	$14.44	7.794%	$15.5655	$15.57	$15.55	$15.60
Purchase #3	$156.62	7.136%	$167.7964	$167.80	$167.80	$167.80
Purchase #4	$52.86	9.440%	$57.85	$57.85	$57.85	$57.90
Purchase #5	$105.58	3.243%	$109.004	$109.00	$109.00	$109.00
Purchase #6	$66.83	5.317%	$70.3834	$70.38	$70.40	$70.40
Purchase #7	$34.90	7.675%	$37.5786	$37.58	$37.60	$37.60
7 purchase totals =	$556.69		$590.9422	$590.94	$590.95	$591.10