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	$178.43	6.438%	$189.9173	$189.92	$189.90	$189.90
Purchase #2	$13.98	5.303%	$14.7214	$14.72	$14.70	$14.70
Purchase #3	$80.93	10.710%	$89.5976	$89.60	$89.60	$89.60
Purchase #4	$25.72	7.839%	$27.7362	$27.74	$27.75	$27.70
Purchase #5	$204.38	9.406%	$223.604	$223.60	$223.60	$223.60
Purchase #6	$183.99	6.746%	$196.402	$196.40	$196.40	$196.40
Purchase #7	$20.98	9.848%	$23.0461	$23.05	$23.05	$23.00
7 purchase totals =	$708.41		$765.0246	$765.03	$765.00	$764.90