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	$136.38	6.839%	$145.707	$145.71	$145.70	$145.70
Purchase #2	$240.96	5.772%	$254.8682	$254.87	$254.85	$254.90
Purchase #3	$55.36	13.655%	$62.9194	$62.92	$62.90	$62.90
Purchase #4	$154.53	7.232%	$165.7056	$165.71	$165.70	$165.70
Purchase #5	$40.37	13.855%	$45.9633	$45.96	$45.95	$46.00
Purchase #6	$203.48	6.712%	$217.1376	$217.14	$217.15	$217.10
Purchase #7	$177.37	7.411%	$190.5149	$190.51	$190.50	$190.50
7 purchase totals =	$1,008.45		$1,082.8160	$1,082.82	$1,082.75	$1,082.80