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	$37.25	9.109%	$40.6431	$40.64	$40.65	$40.60
Purchase #2	$82.79	4.675%	$86.6604	$86.66	$86.65	$86.70
Purchase #3	$188.80	3.438%	$195.2909	$195.29	$195.30	$195.30
Purchase #4	$127.79	3.507%	$132.2716	$132.27	$132.25	$132.30
Purchase #5	$10.51	9.208%	$11.4778	$11.48	$11.50	$11.50
Purchase #6	$168.57	6.133%	$178.9084	$178.91	$178.90	$178.90
Purchase #7	$90.93	10.387%	$100.3749	$100.37	$100.35	$100.40
7 purchase totals =	$706.64		$745.6271	$745.62	$745.60	$745.70