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	$112.84	12.603%	$127.0612	$127.06	$127.05	$127.10
Purchase #2	$70.93	5.719%	$74.9865	$74.99	$75.00	$75.00
Purchase #3	$145.47	5.426%	$153.3632	$153.36	$153.35	$153.40
Purchase #4	$54.94	7.488%	$59.0539	$59.05	$59.05	$59.10
Purchase #5	$145.44	3.445%	$150.4504	$150.45	$150.45	$150.50
Purchase #6	$144.92	6.839%	$154.8311	$154.83	$154.85	$154.80
Purchase #7	$48.54	4.270%	$50.6127	$50.61	$50.60	$50.60
7 purchase totals =	$723.08		$770.3590	$770.35	$770.35	$770.50