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	$64.36	9.371%	$70.3912	$70.39	$70.40	$70.40
Purchase #2	$23.31	9.816%	$25.5981	$25.60	$25.60	$25.60
Purchase #3	$173.56	7.447%	$186.485	$186.49	$186.50	$186.50
Purchase #4	$174.62	12.301%	$196.1	$196.10	$196.10	$196.10
Purchase #5	$95.64	6.638%	$101.9886	$101.99	$102.00	$102.00
Purchase #6	$56.50	5.217%	$59.4476	$59.45	$59.45	$59.40
Purchase #7	$195.46	12.748%	$220.3772	$220.38	$220.40	$220.40
7 purchase totals =	$783.45		$860.3877	$860.40	$860.45	$860.40