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	$108.95	13.598%	$123.765	$123.77	$123.75	$123.80
Purchase #2	$18.65	8.862%	$20.3028	$20.30	$20.30	$20.30
Purchase #3	$210.90	6.380%	$224.3554	$224.36	$224.35	$224.40
Purchase #4	$142.50	5.647%	$150.547	$150.55	$150.55	$150.50
Purchase #5	$36.83	9.836%	$40.4526	$40.45	$40.45	$40.50
Purchase #6	$63.64	3.635%	$65.9533	$65.95	$65.95	$66.00
Purchase #7	$108.57	10.325%	$119.7799	$119.78	$119.80	$119.80
7 purchase totals =	$690.04		$745.1560	$745.16	$745.15	$745.30