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	$181.34	10.698%	$200.7398	$200.74	$200.75	$200.70
Purchase #2	$173.67	5.441%	$183.1194	$183.12	$183.10	$183.10
Purchase #3	$79.95	6.849%	$85.4258	$85.43	$85.45	$85.40
Purchase #4	$189.78	3.735%	$196.8683	$196.87	$196.85	$196.90
Purchase #5	$159.93	11.106%	$177.6918	$177.69	$177.70	$177.70
Purchase #6	$177.98	10.524%	$196.7106	$196.71	$196.70	$196.70
Purchase #7	$246.71	4.523%	$257.8687	$257.87	$257.85	$257.90
7 purchase totals =	$1,209.36		$1,298.4244	$1,298.43	$1,298.40	$1,298.40