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	$125.81	6.418%	$133.8845	$133.88	$133.90	$133.90
Purchase #2	$187.28	13.843%	$213.2052	$213.21	$213.20	$213.20
Purchase #3	$214.71	4.306%	$223.9554	$223.96	$223.95	$224.00
Purchase #4	$88.83	13.188%	$100.5449	$100.54	$100.55	$100.50
Purchase #5	$90.37	5.527%	$95.3647	$95.36	$95.35	$95.40
Purchase #6	$101.37	13.384%	$114.9374	$114.94	$114.95	$114.90
Purchase #7	$105.54	5.668%	$111.522	$111.52	$111.50	$111.50
7 purchase totals =	$913.91		$993.4141	$993.41	$993.40	$993.40