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	$24.25	6.757%	$25.8886	$25.89	$25.90	$25.90
Purchase #2	$38.51	5.335%	$40.5645	$40.56	$40.55	$40.60
Purchase #3	$89.50	8.358%	$96.9804	$96.98	$97.00	$97.00
Purchase #4	$104.37	13.432%	$118.389	$118.39	$118.40	$118.40
Purchase #5	$221.92	11.120%	$246.5975	$246.60	$246.60	$246.60
Purchase #6	$59.51	7.397%	$63.912	$63.91	$63.90	$63.90
Purchase #7	$105.56	7.551%	$113.5308	$113.53	$113.55	$113.50
7 purchase totals =	$643.62		$705.8628	$705.86	$705.90	$705.90