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	$24.68	3.817%	$25.622	$25.62	$25.60	$25.60
Purchase #2	$99.90	5.238%	$105.1328	$105.13	$105.15	$105.10
Purchase #3	$74.79	13.187%	$84.6526	$84.65	$84.65	$84.70
Purchase #4	$87.29	13.207%	$98.8184	$98.82	$98.80	$98.80
Purchase #5	$193.43	12.733%	$218.0594	$218.06	$218.05	$218.10
Purchase #6	$70.50	11.497%	$78.6054	$78.61	$78.60	$78.60
Purchase #7	$63.41	6.513%	$67.5399	$67.54	$67.55	$67.50
7 purchase totals =	$614.00		$678.4305	$678.43	$678.40	$678.40