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	$84.64	9.398%	$92.5945	$92.59	$92.60	$92.60
Purchase #2	$52.63	5.420%	$55.4825	$55.48	$55.50	$55.50
Purchase #3	$170.38	7.509%	$183.1738	$183.17	$183.15	$183.20
Purchase #4	$119.41	6.818%	$127.5514	$127.55	$127.55	$127.60
Purchase #5	$172.60	12.142%	$193.5571	$193.56	$193.55	$193.60
Purchase #6	$133.90	13.206%	$151.5828	$151.58	$151.60	$151.60
Purchase #7	$133.94	12.693%	$150.941	$150.94	$150.95	$150.90
7 purchase totals =	$867.50		$954.8831	$954.87	$954.90	$955.00