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	$37.61	4.480%	$39.2949	$39.29	$39.30	$39.30
Purchase #2	$82.87	3.734%	$85.9644	$85.96	$85.95	$86.00
Purchase #3	$140.78	8.514%	$152.766	$152.77	$152.75	$152.80
Purchase #4	$150.72	8.541%	$163.593	$163.59	$163.60	$163.60
Purchase #5	$88.43	12.517%	$99.4988	$99.50	$99.50	$99.50
Purchase #6	$21.43	5.686%	$22.6485	$22.65	$22.65	$22.60
Purchase #7	$118.51	10.213%	$130.6134	$130.61	$130.60	$130.60
7 purchase totals =	$640.35		$694.3790	$694.37	$694.35	$694.40