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	$82.26	7.858%	$88.724	$88.72	$88.70	$88.70
Purchase #2	$52.91	12.499%	$59.5232	$59.52	$59.50	$59.50
Purchase #3	$57.58	8.135%	$62.2641	$62.26	$62.25	$62.30
Purchase #4	$250.81	3.843%	$260.4486	$260.45	$260.45	$260.40
Purchase #5	$89.33	4.638%	$93.4731	$93.47	$93.45	$93.50
Purchase #6	$203.60	12.241%	$228.5227	$228.52	$228.50	$228.50
Purchase #7	$88.65	6.517%	$94.4273	$94.43	$94.45	$94.40
7 purchase totals =	$825.14		$887.3830	$887.37	$887.30	$887.30