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	$180.27	9.161%	$196.7845	$196.78	$196.80	$196.80
Purchase #2	$89.34	10.247%	$98.4947	$98.49	$98.50	$98.50
Purchase #3	$100.75	12.729%	$113.5745	$113.57	$113.55	$113.60
Purchase #4	$25.69	13.686%	$29.2059	$29.21	$29.20	$29.20
Purchase #5	$17.79	4.383%	$18.5697	$18.57	$18.55	$18.60
Purchase #6	$116.47	9.752%	$127.8282	$127.83	$127.85	$127.80
Purchase #7	$32.97	9.334%	$36.0474	$36.05	$36.05	$36.00
7 purchase totals =	$563.28		$620.5049	$620.50	$620.50	$620.50