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	$186.28	11.653%	$207.9872	$207.99	$208.00	$208.00
Purchase #2	$175.95	12.731%	$198.3502	$198.35	$198.35	$198.40
Purchase #3	$241.35	9.808%	$265.0216	$265.02	$265.00	$265.00
Purchase #4	$145.71	5.360%	$153.5201	$153.52	$153.50	$153.50
Purchase #5	$59.46	13.672%	$67.5894	$67.59	$67.60	$67.60
Purchase #6	$75.49	4.169%	$78.6372	$78.64	$78.65	$78.60
Purchase #7	$43.82	8.584%	$47.5815	$47.58	$47.60	$47.60
7 purchase totals =	$928.06		$1,018.6872	$1,018.69	$1,018.70	$1,018.70