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	$197.51	6.627%	$210.599	$210.60	$210.60	$210.60
Purchase #2	$216.33	3.315%	$223.5013	$223.50	$223.50	$223.50
Purchase #3	$139.39	13.605%	$158.354	$158.35	$158.35	$158.40
Purchase #4	$100.68	8.841%	$109.5811	$109.58	$109.60	$109.60
Purchase #5	$133.51	7.441%	$143.4445	$143.44	$143.45	$143.40
Purchase #6	$204.52	9.138%	$223.209	$223.21	$223.20	$223.20
Purchase #7	$87.58	11.750%	$97.8707	$97.87	$97.85	$97.90
7 purchase totals =	$1,079.52		$1,166.5596	$1,166.55	$1,166.55	$1,166.60